These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Sword Art Online
Alternative Character Interpretation: Kirito isn't as Oblivious to Love as he appears; he figured out that Lizbeth had feelings for him. In the case of Asuna, he does have feelings for her, and he recognizes the signals she's sending out, but he's still getting over the trauma of Sachi's death.
There's also an in-universe example with Kirito, whose "loner" attitude is interpreted early by many players as a sign of him being a "Beater" and not caring about other players, while in reality it is caused by his Survivor Guilt and fear of losing any more people; if anything, the way he treated Klein and Asuna (he is the one because of whom they started Taking Levels In Badass) and him taking the blame for other beta-testers after the first boss' defeat make it really hard to see him as a selfish type unless this trope is invoked.
Keita blaming Kirito for their guild-mate's deaths is in fact a mental defense mechanism for his Survivors Guilt. In truth, he blames himself for not being there. Yet he doesn't even believe himself, which is why he kills himself right afterward.
The second OP "INNOCENCE" (performed by Eir Aoi) and the second ED "Overfly" (performed by Luna Haruna) might just top the first OP and ED in terms of awesomeness.
In the actual OST, special mention to "Swordland", which sounds in the most climatic action moments. It became the most iconic theme of the series, by far.
"Luminous Sword", Asuna's combat theme. This is a classic Kajiura-style theme that fits the main female lead to a T.
"False King". Yeah, yeah, make all the "EPIC RAPE MUSIC!" jokes you want. That doesn't make this theme any less awesome! Plus, the theme has its chance to shine, free from the Squick factor, during the scene where Kirito beats Sugou in real life.
Everything about the Official Couple Kirito and Asuna. For Kirito it mostly has to do with whether or not he is a blatant Marty Stu and bland Wish Fulfillment as opposed to being a completely legitimate and competent badass lead anime hasn't seen in years. Asuna is either the most moe and likable character in recent anime history or a Mary Sue and another typical Shana Clone. Some claim that both are a little bit too perfect, thus making them unrelatable, if not downright unlikable.
How Kirito and Asuna work as a couple have similar reactions. Some see it as a cute, incredibly heartwarming classic romance between two truly likable characters with genuine chemistry, which is the true central pillar of the story. Others see it as a saccharine, melodramatic and non-believable couple, created by a teenager who writes how he thinks relationships work, which's only there for even more Wish Fulfillment (See Romantic Plot Tumor below).
On the same note, is Kirito and Asuna's Romance Arc developed enough? Detractors usually consider Episode 8 the beginning of the arc, so they say it doesn't have nearly enough development to be believable that they fall in love. Kirito's interactions with his Supporting Harem before then don't help either. Defenders, on the other hand, consider that it actually starts in Episode 2, and that even if their relationship is not the A plot, their interactions and Belligerent Sexual Tension prepare the terrain for when the romance jumps to the forefront. The constant hints that they keep meeting off screen for months (Not a Date included) also help.
And finally, is their relationship a blatant and saccharine Romantic Plot Tumor that utterly ruins the awesome premise of the story? Or does it actually add to it, giving it real emotional stakes and creates an incredibly compelling mix between action, adventure and romance that is so hard to find in anime?
Who deserves Kirito more? Asuna vs. his Supporting Harem. For some, the Kirito and Asuna relationship lacks chemistry and development, especially in the anime.
Whether or not Kirito and Asuna actually had sex. They do in the light novels (rather explicitly, in a scene some consider to be Squicky) but the anime is much vaguer.
The series has an Awesome Music entry for good reason... although some people may argue that it sounds a little bit too similar to Yuki Kajiura's previous works. Others say that the compositions are great, but the best tracks (particularly Swordland) are so overused that they eventually get old.
Quite a few fans have said that SAO is a good Gateway Series to anime, however, many of its detractors have said otherwise and accused it of being heavy on "Otaku pandering" and Wish Fulfillment. This was a point of contention by some fans on whether it should air on Toonami or not, due to the said block's status as a gateway drug to the medium. Ultimately, the block’s creators thought the negative aspects weren’t a big deal.
Complete Monster: Sugou, the Big Bad of the Fairy Dance arc. He imprisoned 300 SAO players, including Asuna, into a virtual prison, and conducted mind control experiments on them. And then if that wasn't enough, he intended to rape Asuna in ALO, and then in the real world, while she's still comatose. And as the last straw, he tried to kill Kirito in the real world.
Sugou: "First, I'll take the purity of your heart, then the purity of your body."
XaXa and Johnny Black from the GGO arc. A pair of Player Killers from SAO, they decide, after escaping into the real world, that they need to keep on killing. XaXa hijacks his mentally unstable brother's plan to create the ultimate gunslinger, arranging for opposing players to be poisoned in the real world, at the same time that their avatars are shot in the virtual world. Johnny is his ally in this, killing two of the four victims, and subsequently trying to kill Kirito and Asuna himself after XaXa's imprisonment. This is without taking into account their plans to torture three opposing players to death during SAO. A pair of reprehensible sadists, with the highest onscreen bodycount of any character in the series, XaXa and Johnny are about as low as gamers can get.
Critical Backlash: Not surprisingly, an increasing amount of folks are saying that the hate and backlash for the show and especially Fairy Dance is quickly reaching this territory. This is actually the opinion of Toonami themselves (whom probably witnessed first-hand many requests of SAO coming to the block get retracted when the show moved on to Fairy Dance during it's airing in Japan), as their rational for picking it upin response to the backlash.
Designated Hero: A Marty Stu he might be, but Kirito is always sympathetic enough to avoid falling into this role... until the climax of the Fairy Dance arc. He's given himself GM powers! He's about to save Asuna! He's got the villain at his mercy! And what's the first thing he does? "Set Pain Absorber at level zero." That's right, folks. Kirito brutally tortures Sugou until he's wailing in terror and agony, doing such things as cutting off his arm and stabbing him in the eye. He's clearly suffered serious damage from it, as shown in the next episode when he encounters Kirito in the hospital parking lot. The show interprets this action as heroic; Asuna and Yui don't even look remotely disturbed by Kirito's brutal actions. Even if the victim is a Complete Monster, the show looks like it's endorsing torture and violence as instruments of justice, a message that can be just plain disturbing. Fortunately, Kirito steps back into sympathetic territory by the next episode, when he refrains from killing Sugou and leaves him to the police instead.
Dry Docking: The number of fans that hate Kirito's guts and want him to stay away from ANY female character in the cast so they can have them for themselves is quite high, if we pay attention to the comments about the two tie-in games for PSP and PS Vita (see The Scrappy entry about Kirito below).
On a related note, there's a small number of people who strongly dislike the show but actually really like Lisbeth.
Silica as well, a lot of fans are upset that she doesn't get much screen time in the anime across from Episode 4 and her first episode cameo.
Godfrey, who is killed off after 4 minutes of screentime is this. His bro-ness personality and appearance reminds viewers of another Ensemble Darkhorse: Rider.
Klein is a HUGE example. He's one of the most likeable characters in the series because he acts like such a bro to Kirito, yet also shows genuine emotion and is a damn good fighter and guild leader. There's a large amount of fan's who claim HE should be the main character, not Kirito.
Escapist Character: Kirito and Asuna, for people who don't consider them a pairof Sues (or consider them, but don't mind or think it's justified). Although the number of people in this camp decreases dramatically in later arcs, specially the ALFheim storyline.
Fandom Rivalry: Theres has been one with Log Horizon, due to the similar premise. Interestingly enough, many Log Horizon supporters seem to be former SAO fans that dropped the series at some point (normally when the focus of the Aincrad arc shifted to romance, or when the Fairy Dance arc started).
To a lesser extent, there's also one with Accel World, which is written by the same author.
Berserk fans have also not taken well to the fact that "The Black Swordsman" is now more commonly associated with a 16 year old instead of an adult.
.hack fans too are pretty pissed about the fact that SAO is considered super original and "had to be done", when in fact, .hack was released much earlier (though SAO was actually written at about the same time).
First Installment Wins: Despite the story spanning at least four different MM Os, with the titular Sword Art Online only appearing in in a single novel and a handful of short stories, the majority of merchandise and and promotional material use the characters' Aincrad appearance.
Fridge Brilliance: "That's not possible!" said three or four times should probably give you a clue that we don't know something, especially if Kayaba says it about anything anyone does inside SAO. And then we learn about Fluctlight...
"Funny Aneurysm" Moment: It's really hard to laugh when Kirito accidentally grabs Asuna's right breast after seeing Asuna nearly getting raped much later.
God-Mode Sue: There are some complaints that Kirito is this at various points, with some people who agree, some who disagree, and some who agree but think it makes perfect sense in-universe, so they don't care. Invoked during the ALO arc, as Kirito gets gets an Old Save Bonus from SAO (because ALO was built using the same engine as SAO), so he keeps all his old stats, meaning that he is easily the most powerful player in the game the second he starts. Kirito even lampshades it.
Kirito: "I'm not even a beater this time, I'm just a cheater."
Hilarious in Hindsight: The fact that there is an Arc called, "Mother's Rosario." Kirito's birthday is the Feast of the Rosary.
The titular sword arts, as described in the novel, are special attacks where the system briefly takes over limb control, activated by specific arm movements. In other words, waggle controls five years before the Wii popularized them.
Ho Yay: Oodles between Kirito and Klein, starting in the very first episode. In the Japanese version of the first episode...
Klein: Kirito! ...Ah... Hey, Kirito. You were actually pretty cute. That's my type.
Kirito: And that unkempt face of yours suits you ten times better.
Love It or Hate It: One of the biggest anime examples in recent memory. Depending on who you ask, it's either one of the best animes of all time or one of the worst examples of bad writing in existence. And when these two kinds of viewers collide, it ain't pretty.
Moral Event Horizon: Virtually anything Kayaba Akihiko a.k.a Heathcliff does, such as trapping 10,000 innocent people inside a game for TWO YEARS, over which time 4000 of these people died, just to satisfy his game master fantasies. Even worse, he positions himself as the leader of the strongest guild in the game, earning the trust and admiration of many of the people he trapped, with the full intention of betraying them once they neared the end of the game. Kirito even thinks that the guy is a monster during their fight, after seeing how he felt nothing in spite of being responsible for thousands of deaths.
Sugou crossed the line early on, and continues to Kick the Dog after that.
Never Live It Down: The series definitely has Supporting Harem elements to it, but if you were to believe the haters, Kirito spends at least 50% of his screen time picking up chicks without even trying, or worse, being a pimp. The reality is that this particular aspect of the series doesn't have nearly that much of a relevance outside a couple of filler episodes and one or two scenes where it's Played for Laughs. There are also several examples of female characters that don't show any hint of attraction towards Kirito, like Yoruko.
It doesn't help the fact that Reki Kawahara likes to joke about this, like when he said that he feels incapable to write a female character in this series without making her fall for Kirito.
On a similar note, Asuna's Tsundere traits. Albeit they're definitely there, they are prominent only between episodes 5 and 8. However, a lot of viewers talk about her as if she was anime!Naru Narusegawa 2.0. To be fair, she got some problems in the adaptation due to her Characterization Marches On in the light novels (see her entry in the Character page for details).
Chapter 16.5. An infamous exercise in Ikea Erotica that was only posted on the original website's now-defunct fanfic section. The way some are quick to bring it up at the mere mention of the series, you'd think it made for the entirety of the franchise.
And there is always the possibility that when Deep-Immersion Gaming is invented in a decade or two that it won't be as safe as it was intended to be. There are a bunch of ways to die with a Nerve Gear that DON'T involve product tampering. The fact that you're completely paralyzed means that if there was some emergency, such as a fire, you would be completely helpless because you'd have no way of knowing that you were in danger.
Romantic Plot Tumor: Kirito and Asuna. Their relationship practically overtakes the whole escaping the MMORPG storyline, even though it barely has any development.
Suguha's feelings for Kirito/Kazuto in the second half. Getting past the IncestualValues Dissonance, it can come across as unnecessary and only serves to drag the plot down. Specially considering that the audience already knows that, even if they weren't related, there's no way in hell Kirito would have chosen Suguha over Asuna after all they went through together in Aincrad.
Yui gets the most heat, to the point that some believe that she is a lolicon pandering bait, the dreaded moeblob. Many disliked her story arc, as they asserted that the emotion was contrived and pretentious.
Kirito has gotten more and more hate from the fan base with the pass of time, as his ability to make girls to fall in love with him reached almost memetic levels, despite that it's arguably overtly exaggerated (see Never Live It Down above). To give you an idea, the anime has two tie-in games for PSP and PS Vita, and there are quite some fans that say they are interested, but won't play them because they don't want to play as Kirito.
To a lesser degree, Asuna also gets on the nerves of some fans, especially because of her Tsundere traits. Curiously enough, her Distress Ball during the Fairy Dance arc isn't brought up nearly as often. Haters use it more against the writing as a whole, rather than against the character itself.
Ironically, there wasn't the same reaction with Silica in Episode 4 where she was seen in her fanservice underwear.
Suguha was almost INSTANTLY disliked by people for almost everything she did from her wanting to be Kissing Cousins with Kirito, to her genuine lack of combat skills in a MMO, to her repeatedly going "Kirito-kun" in just about every scene she's in, to even her "stealing" the role of the heroine from Asuna.
He is also a Replacement Scrappy for Akihiko Kayaba, not being nearly as cool or magnificent as he was.
Scrub: An in-universe example, any players with an attitude against Beta testers mentioned they saw them as unpunished cheaters who have an unfair advantage in terms of knowledge and getting a head-start can give off this vibe.
Seasonal Rot: Quite a few fans consider the Fairy Dance arc as a down part of the series, especially since it pretty much nullified Aincrad’s emotional conclusion. Asuna was reduced to a Damsel in Distress, and the romantic aspects were focused on Suguha and her feelings for Kazuto/Kirito. When Episode 21 hit, the arrival of Tentacle Rope had the fanbase screaming and Episode 24's Attempted Rape of Asuna in front of Kirito sent most who had stuck with the show until that point nuclear. As a result, quite a few people that have previously praised SAO have switched to bashing the series by the arc's end. In fact, it's quite common to hear the phrase: "I like Aincrad, but hate Alfheim." as a way to basically describe people's viewpoints on the series.
Interestingly enough, this is also applies to some people for the second half of the Aincrad arc, mainly episode 8/9-14. For these people, the two year Time Skip and the switch of focus from the "complete the game" story to Kirito and Asuna's relationship was what started the decline.
Second Season Downfall: There was concerns that due to the backlash of Fairy Dance, the Phantom Bullet arc onwards wouldn't be realized. Fortunately, this was averted as a second season came out in the summer of 2014. Whether Phantom Bullet will eventually be dubbed and air on Toonami is still up in the air, however.
Snark Bait: By the time the second season started, SAO had become one of the biggest ones in the entire anime community. Specially among critics. Some even said that they enjoyed seeing how the first season failed to meet its potential. The Fairy Dance Arc gets the majority of the flak, albeit the Aincrad arc doesn't get a complete free pass either.
Squick: The Attempted Rape on Asuna. The act itself was already bad enough to Squick a lot of fans, even to the point of making them to drop the show. But it's even worse in how it's portrayed: The way Kirito saves her is seen by many as an empowerment fantasy. Even people who don't mind the Wish Fulfillment aspects of the show think that Kawahara went way too far in that scene.
Mind you, Sugou was squicking the audience since his very first appearance. Just the way that he sniffed Asuna's hair in the hospital with that sick smirk on his face is enough proof that his Complete Monster label was never meant to be a surprise reveal.
Tastes Like Diabetes: Yui. Fans thought that she was adorable and contributed to Kirito and Asuna's relationship. Detractors on the other hand saw it as contrived and pretentious and say it contributed to the show's Seasonal Rot.
Debatable sure, but some of Kirito and Asuna's scenes where they are being a couple can really come across this way due to some rather cheesy, if not just down right cringe worthy lines.
They Wasted a Perfectly Good Character: Klein is introduced in the first episode as a new player who Kirito somewhat befriends. The two separate by the end but instead of making use of Klein by having him possibly a Foil to Kirito (Mainly because Kirito fails to save the first guild he joined, Klein protected his whole guild through SAO), and him being a active ally in the series, instead Klein serves mainly a comic real character with not much characterization beyond being "Kirito's buddy".
They Wasted a Perfectly Good Plot: The first three episodes deal with an interesting premise, thousands of players trapped in an online death game by a madman. Then the plot chomps forward with Kirito friend-zoning multiple teenage girls and falling in love. Then there's a little sister who's attracted to her big brother, and a copy cat death game and... ugh. To put it simply, it's not as self-contained as the premise would imply.
Similarly Kirito at one point mentions how life for everyone in the game is starting to be the norm and people don't mind it as much. Instead of using this to show the deep immersion of the game through Kirito and Asuna in a discussion or something, it's just used as throw away idea.
Kayaba Akihiko's reasoning for why he trapped the players in SAO was never explored and why he did the things he did is never fully gone into detail besides him basically saying "I did it cause I could", which wouldn't be a bad reasoning, if it wasn't for the fact that he hints at other reasons.
Values Dissonance: Shino Asada attacked a bank robber who was about to shoot her mother, and manages to kill the full-grown man with his own gun - years before the events of GGO, in which she was sixteen. In America, that Crowning Moment Of Awesome would make her a hero of nation-wide acclaim, but this is Japan, where guns are considered more horrible than child pornography (Not Hyperbole). She is ostracized by just about everyone, including her own mother. This even extends to therapists who learned of the event, so she has a case of PTSD so intense that a schoolyard bully can set off a panic attack simply by pointing a finger at her and saying "bang".
What an Idiot: Sugou's ego and Card-Carrying Villain -ness makes him quite Genre Blind and he made many mistakes that were entirely avoidable had he just coldly thought and calculated about it like Kayaba. Sugou could have kept up a facade to everyone, not just Asuna's parents, or in general just not talk and gloat. Or he could've used a private server for testing instead of wanting to play god. Or he could've used something other than keypad and card for lock. Or he could've used GM ban/delete as soon as things went downhill. If he had down any of these, he would've got away with everything. But he didn't, and this led to Kirito rescuing Asuna and Sugou in jail.
Supplemental material shows that Silica's dragon Pina would have become his mount and a sub-boss.
Asuna reveals to be one, having no-one else but Kirito in her life. And beyond that, was one of three hundred unfortunate players who never woke up after the SAO ordeal, being forced to be with Sugou, then proceeds to be nearly raped by him. Someone help this poor girl out!
Her backstory is expanded in later novels and the manga, which reveal that the reason why she's alone in the world before knowing Kirito is because of her high class family, who was extremely strict and put almost unrealistic expectations on her. Especially her mother, who originally comes from a low class family, and started to live through her. It is implied that the reason she entered the game was to escape from all that pressure.
Kirito isn't much better. Although he woke up, he discovers that his love never woke up, still comatose, only to find out that it had been planned.
And before that, the emotional pain he went through after Sachi, his previous love before Asuna, dies.