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: Lyrical Nanoha
YMMVs for the franchise as a whole: (for specific ones go to the corresponding season's YMMV page)
Audience Alienating Premise: It's a Magical Girl series aimed at young adult men. Moe is de rigeur for most anime, but the cutesy imagery can be a turnoff for American (and some Western) audiences that don't look beneath the surface to the action series within.
Broken Base: With the exception of A's, which is considered an Even Better Sequel, pretty much any other entry into the main continuity has left the fandom polarised. It doesn't help that the author is constantly tinkering with the established formula in very unsubtle ways.
StrikerS caught flak for having a 10 year timeskip, thus losing most of the lolis. It moved the setting away from Earth and shifted focus from the previous main characters, (demoting several to extras in the process), to a bunch of rookies and a lot more non-essential background characters. The Numbers cyborgs probably got the most heated debates among the fandom as to whether they were credible antagonists compared to the very powerful rivals from seasons one and two. They were also not as well-developed as previous antagonists, probably because there were so many of them. The third season was twice as long as previous seasons, but rather than using that extra time to develop its enormously expanded cast or give screentime to those characters inexplicably shoved out of the picture, the writers instead devoted most of the episodes to training the newbies and discussing military policies.
Sound Stage X was basically a continuation of StrikerS... with no characters introduced before that season making any appearances. People who were not fans of the new characters did not take it well.
ViVid was the first installment to shift from anime to manga, and a monthly one at that, so it already had a strike against it before it even started. Then it turned out it was a Lighter and Softer take on the series with plushy devices, no interdimensional incidents, Magical Girl tropes played straight and more lolis (and loli fanservice) than ever. It actually reads more like a shonen series with magical girls... and no antagonist so far. People who liked the changes in StrikerS were disappointed, but in Japan where moe is the law it's the most successful entry in the franchise yet.
And then there's Force. If StrikerS broke the base, than Force Starlight Breakered what was left of it. Running concurrently with ViVid, it went completely the other way, all but ensuring that fans of one series hated the other and vice versa. It dropped most magical girl tropes altogether, introduced a bunch of new characters yet again, including an angsty male lead, which was the last thing anyone expected. It only keeps getting Darker and Edgier - innocent people are dying in bloody ways, antagonists are killing indiscriminately for fun, fan-favourite characters are being curb stomped left and right with powers that seem more than a little broken and the weaponsandarmordesignsarenow approaching Warhammer 40000 levels of batshit insane. People think it's either the most awesome thing ever or a Dork Age that never happened.
All of this is just from the main series. If we add the alternate continuities, we can also mention:
The movie, which was accused by some of being an unoriginal rehash of season one with half the plot and twice the explosions and cutting out pretty much anyone that wasn't Nanoha, Fate or Precia. Others liked it for exactly the same reasons.
The movie manga, which later turned out to have little to do with the movie and more in common with the light novel. It was widely decried for the perceived change in character of Nanoha (or Emoha as this version is known to the western fans) and generally trying to be too dramatic with the brutal fight scene between Nanoha and Fate that lasted for most of the second volume. And despite being an Alternate Universe that changed many things along the way, it still ended the exact same way as the original anime and the movie, leaving many to wonder what the point of it was.
The Fate/stay night crossover, which disappointed people who were expecting something serious and longer than a one-shot.
TheBattleOfAces was generally well-received for shifting the focus back to the A's characters and the introduced Evil Twins of the main characters became popular enough to be included in the sequel, but even most of its fans admit that it was mediocre in terms of gameplay.
The Sequel to the above game The Gearsof Destiny almost broke this trend. The game have a stronger AI, great amount of playable characters, and a good story with good character development. However the Manga cast contribute next to nothing to the overall main story, and the ending used Laser-Guided Amnesia to preserve the timeline. But how could this preserve the timeline when the two Timetravelers took four people from the current time era with them? It feels like they are trying to invoke In Spiteofa Nail to make this timeline completely similar to the main one. It left the feeling of The movie manga all over again.
Previews and Info started showing up for the Second Movie base on A's. People are already complaining about the changes such as replacing Nanoha and Fate's reunion from Big Damn Heroes to Hugging. Removing Yuuno from battle, and most likely be replace by Lindy. And Removing the Liese twin altogether. Some fans are saying "Please let this be good." others are thinking "It cannot be as good as the original TV Series. How worst will it get?"
Hilarious in Hindsight: Would you believe this was the prototype for the series. If you've watched the show for any length of time, the sight of Nanoha waving around that puny heart-shaped wand alone will be enough to make you crack up.
Just Here for Godzilla: Subverted. Before the first season's Growing the Beard moment, viewers were expected to just be there to see cute little Nanoha from Triangle Heart 3: Sweet Songs Forever in a strange alternate universe. They were quickly disproven when Nanoha got more viewers than the Triangle Heart 3 OVA. Ever since Nanoha became the perfect example of More Popular Spin-off, to the point where anyone looking for Triangle Heart 3 is probably just there to see Nanoha in a strange alternate universe.
Rescued from the Scrappy Heap: As time passed, reception of Precia Testarossa has lightened, especially in presence of the much reviled Huckebeins, and then she got Woobie moments in the 1st movie, then Gears of Destiny reveal another of her tender side shown towards Linith, THEN she suddenly becomes a loving mother in INNOCENCE. Really way to go when back in the days, she really is the bonafide "Most despicable, worst mom ever" with evil acts to prove it.
They Wasted A Perfectly Good Character: YUUNO. In a series so focused on how the ancient civilizations and technologies of the past are enormously impacting upon the present day, having an archeologist, scholar and librarian of ancient knowledge in the cast would seem like a great idea. If nothing else, Yuuno could have continued his roll as Mr. Exposition in StrikerS, Sound Stage X, ViVid and Force, considering that no one would be better qualified to explain about the Belkan Reunification War, the Sankt Kaiser dynasty, the Saint's Cradle, the Hegemon Klaus and his relationship with Olivie, Queen Ixpelia and the Mariage, and perhaps even the Bible of the Silver Cross and its Eclipse Virus.