Awesome Music: Duh. It's about time that the series' track record finally gets used as it deserves. Only this time, given the game's based on music, the developers aren't really allowed to screw up. Chris Kohler, of Wired and Power-Up full title: "Power-Up - How Japanese Video Games Gave The World An Extra Life" fame, put it best:
Chris Kohler: "If it sucks, itíll really suck."
The remixes of the Kingdom of Baron, Hunter's Chance and Loss of Me/Something to Protect.
Squeenix seems to have taken advantage of this and saved some of the best tracks as DLC, such as Dark Messenger and (any) of the final battles except some such as II and VI's.
The final boss theme is a remix of the original Chaos Shrine theme, given much more grandeur and intensity to make it suitable for your final battle. And it is glorious.
Hell, the Hi-Fi remix of Battle on the Big Bridge that plays at the song select screen of the iOS version qualifies.
Base Breaker: In Curtain Call, either you find Mog's voice in the VS to be a Most Annoying Sound and very distracting (Though thankfully for those people it does have an off option) or you find it adorable (as well as adding to the atmosphere) and quite useful. Then again Moogles have always been one of the biggest "You love them or hate them" in the fandom and the usefulness of Mog's voice is situational as he's very helpful when announcing what EX Burst is being used against you (since looking away from the action to see makes it very easy to miss a note) while endless repetitions of, "They've taken the lead, kupo!" during a very close match make one want to strangle him. Also see Stop Helping Me! below.
Breather Level: Apparently played straight but ultimately averted for DLC song "Shadowlord" from Nier on Ultimate as the first 2/3 of the song are at an even tempo and nodes are spaced apart with only about 200 nodes, then you get the remaining 300 in the last 1/3 of the song. It can be considered the easiest of the 5 longest songs in the game though.
Each of the original 13 base characters has a Limit Break type ability learned at Level 40. For Warrior of Light, Firion and Terra, it activates when you chain so many notes in BMS, and respectively reduces damage by half, restores HP for every successful note trigger, or triples the damage of offensive Magic. Lightning got an ability to boost Strength and Magic by 75 each, and the other nine got a super-attack that they use against bosses and do heavy damage based on their stats, and they will use it against every boss if you do well enough to meet more than one. If it sounds like these abilities are good, they are. With as little as two of the damaging abilities on the right characters at Level 99, the bosses that are supposed to be the toughest enemies in the stage will die on arrival, Warrior of Light and Firion make stages much easier, and Terra's offensive magic is brutal. The developers apparently took notice how good they are, because these abilities were removed from the iOS port. Every character with one in the first game still has theirs in the sequel, and a large number of the new characters have one as well, although since the Quest Medley boss stages require you to defeat the said boss at least once or you lose even if you finish the song, they're more of a necessity as opposed to something that trivializes bosses.
The CollectaCards in the sequel are essentially this: unlike in the first game, where they existed only for collecting them, you can now use them to boost characters' stats far beyond what normal leveling up with allow, especially if you group them together to guarantee higher boosts. With high enough stats, you can basically create a team based entirely around tanking constant enemy attacks from missing every note and using counterattacks to defeat them to gather a huge amount of drops without actively playing the game at all, but doing this is an extremely time-consuming process.
Terra is even more broken in Curtain Call thanks to the opportunity to raise max CP to 99. With at least 68 CP she can equip Trance, Dualcast and Ultima, which is cast when a boss appears. With 6x the normal magic damage she can not only one-shot the boss but do enough damage to kill the enemies that appear after it as well!
Though it takes a whopping 91 CP to pull off, equipping her with Trance, Firaga, Thundaga, and Blizzaga will guarantee that nothing survives for long in a BMS. Team her up with three characters that have Added Cut and there will rarely be an enemy that lasts for more than a few seconds.
Good Bad Bugs: In Field Music (only), letting go of holds late still results in a Critical, as long the vertical position is good enough and you don't hold it so long as to get a miss.
Also, some of the wave-shaped holds can be performed by simply holding rather than making tiny up/down movements. If the release trigger is higher or lower, a gentle slide up or down while holding will still catch all the midpoints with a Critical.
Defeating Chaos and seeing the end credits requires you to get 10000 Rhythmia in the first game, which can be done in a few hours. However, unlocking all the content in the game takes much, much longer: you keep getting new stuff every 500 Rhythmia until you reach 99999, and you can only get around 130+ per song if you do well. While you might be able to get all the shards to unlock every character much faster from Dark Notes and silly titles, songs for the sound test and movies for the movie player might not hold much value for you, you still need at least 45000 Rhythmia to unlock the last extra song in Challenge mode.
In the sequel, this is both improved and made worse: Chaos doesn't challenge you until you reach 20000 Rhythmia and due to the vastly increased number of songs, you probably haven't gone through more than half of them at that point. Furthermore, the first 10 character unlocks are essentially free once you reach the respective Rhythmia amounts, and every Quest Medley you beat for the first time is guaranteed to drop at least 3 shards of any given color. On the other hand, everyone outside of the initial party of 4 needs to be unlocked seperately and Rhythmia goes up to 6 digits, with the last unique unlock gotten at 300000. Thankfully there's a number of ways to get increased amount of Rhythmia per song and the last song unlock has been moved to 40000 Rhytmia.
It's the Same, Now It Sucks: Some people don't like the fact that the tracks are not remixed except for only a few exceptions such as Mt. Gulg, with this particular example being taken from the various remakes of the first game instead of the original 8-bit version. Given that the game is meant to be a tanker truck of nostalgia fuel though, this is more than likely intentional.
Mad Libs Dialogue: While loading a game stage, the game will show your four chosen characters say a part of several phrases they're known for in their proper game, combined into a single sentence. This results in some pretty... bizarre phrases.
Curtain Call has "We Have Arrived", the background FMV being the opening with Milites's rather brutal invasion of Rubrum and Class Zero's death. However this is fixed in the English versions where Final Fantasy Type-0 HD has yet to be released; the ending scene is replaced by Alexander's Light of Judgment attack.
Porting Disaster: In addition to being laggy on anything older than an iPad4 or iPhone5S, the nominally "free" iOS version only includes 2 songs and 13 characters, and purchasing everything costs more than three times as much as the 3DS version — which already includes all of this premium content, except for some songs which are either still DLC or just not available as well as some characters that don't have any unique skills available to them. And oh, no Event Music Stages, one of the biggest draws of the game. On the other hand, some players consider the higher resolution graphics and higher quality music an acceptable tradeoff, especially since DLCs for the 3DS version of the game are No Export for You to those living in areas without the 3DS eShop (when comparatively, the iOS version and all it's DLCs are available worldwide), and rationalizes by buying only the songs and/or song packs they like. Additionally, all iOS devices have a capacitive touch screen compared to the 3DS' resistive touch screen, and the screen itself is bigger to boot (especially on an iPad), making it a little easier to play.
In the first game, the Stoic Bonus is a bit of an odd mechanic. Putting on equipment makes songs a little easier to survive and\or lets you earn more items (depending on what you equip), without affecting your score. Removing all equipment results in a huge score bonus (about 2 letter grade's worth). So the game creates a choice between playing with equipment so you can get more items, or playing without equipment so you can get a better high score. Playing stoic also removes the special features from the songs. Thankfully, it's been removed in the sequel and you can now get a maximum score on any song right off the bat regardless of equipment if you do well enough.
In the first game, getting a Critical on a note once was enough to count it towards completion of the Total Critical chart (and the Practice mode of the song showed which notes hadn't been hit yet). The second game changed it to needing to get nothing but Critical notes for an entire 1/20 of the song that the bars in the chart represent. For bars late in long songs like Dancing Mad and One-Winged Angel, having to play through the whole song to make a single attempt on that one segment gets very tedious if they're especially tricky. The last 15% of Dancing Mad alone is harder than the rest of the song combined.
Button Mode in FMS stages that have a lot of Holds that end with Arrow nodes as holding the circle pad up/down to follow the Hold trail tends to also trigger the arrow at the end prematurely.
Out of all the Ex Bursts in the second game, Judgment seems to be the most hated one. It makes every non-Critical note count as a Bad, it makes the timing for a Critical even stricter than normal and every Bad scored while it's active also causes you to lose points, while none of the other Ex Bursts directly affect the score for the notes you screw up. It's basically the musical equivalent of a Blue Shell.
Although relatively accepted in the first Theatrhythm game, the EMS levels in Curtain Call feel MUCH more difficult to Perfect Chain and All Critical than those in the first game. It doesn't help that, even on Ultimate, most of the EMS levels don't have that many notes, making it very hard to get higher than an S rank on them unless your timing is flawless.
Stop Helping Me!: If you're in a VS match and the the score remains just 1 note shy of a tie (such as 1 person having a single Great vs. all Critical notes), expect Mog to endlessly announce, "They've taken the lead, kupo!" until the difference in scores becomes much greater since the score needle repeatedly touches the exact center then dips towards the one in the lead and the AI is programmed to make the announcement once the needle leaves the center spot rather than cross over entirely after leaving it once.
Surprise Difficulty: The game is full of sparkles, cute cartoon characters, brightly colored and rounded icons, and aside from maybeBarbariccia and some of the more frightening enemies like the Ahriman and Anima, there's nothing a Moral Guardian would object to. The higher difficulty songs will crush your spirit, trample the shards laughing, and invite you back to more. You will wish for the comparatively simple task of just fighting Omega and Shinryu like normal, rather than getting a perfect 200-Critical chain on Ultimate Difficulty with no abilities and starting over any time your timing is off just enough to miss that one Critical.
Tastes Like Diabetes: Chibi Vivi, especially when he hops and swings his little staff. Add the fact he might appear on the main menu and say his quotes from his game.
If playing the songs in game order on Ultimate, Battle With The Four Fiends will make you cry; and that's not even nearly as hard as Battle at the Big Bridge.
And those are just among the songs that are part of the main game. Some of the DLC songs on Ultimate continue to reach a new level of evil each week. In fact, Battle With The Four Fiends and Battle at the Big Bridge may seem easy compared to some of the tracks below...
In Curtain Call, "Dancing Mad" is changed up from its arrangement in the first game, with the final 15% of the song being much harder to Perfectly Chain and Total Critical than the rest of the song combined on Ultimate. The fact that it's one of the longest songs in the game doesn't help either.
Several of the vehicle levels in Curtain Call are also nightmarish on Ultimate (particularly FFXII's "Heart of a Child") as well since the often-fast paced "travel" music allows for very little time to rest between one section of notes and the next.
In a few forums, the hardest levels have been noted to be "Force Your Way" (FFVIII) and "Crazy Chocobo" (FFXIII-2).
Similarly known and feared for their difficulty on Ultimate are "Battle 2" (FFIX) and "Heart of Chaos" (FFXIII-2). And the DLC provides plenty of challenge as well (such as the aforementioned "Crazy Chocobo"), with "Assault" (FFX) and "He of the Name" (Bravely Default) being examples of songs with extremely difficult second halves.
That One Sidequest: In the first game, the trophy for defeating Chaos in a Dark Note. First, he only appears in Dark Notes that are at least level 90 (out of 99). Second, he's always Boss No. 3. Third, he doesn't always appear in a Dark Note of that level, so a player may have to clear through dozens of level 90+ Dark Notes to find him. Fourth, presuming you do find him, he has a ton of hit points, which means you need a lot of power and abilities to clear through him. Fifth, the spinning arrows mentioned under Scrappy Mechanic are guaranteed to appear during the fight. And, finally, he does a ton of damage, so a couple of missed notes can mean having to start over. It's like combining a Metal Slime with a Final Boss, and mixing in a Scrappy Mechanic for a garnish. Good luck.
The second game has the trophy for defeating every enemy at least once. The problem is that several are only rare bosses on Chaos Notes that are at least level 90 - see above about the problems about getting them to randomly drop. Plus, they have a chance to invoke the dreaded spinning slide triggers in the fight. Of course, the rarest ones not only have tons of hit points, but they have a habit of appearing on really short BMS songs. The only saving grace is that there's an item (the Gambler's Soul) that will randomly change a song to a different song of the same type. Sure, it's not necessarily easy to suddenly change to "Dancing Mad" or "One-Winged Angel," but both are long enough, and have enough triggers, to greatly improve your odds of being able to do enough damage.