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.
Ensemble Darkhorse: Finch has a lot of fans especially among readers that aren't entirely convinced of V's virtue.
Genius Bonus: In the film, when V drops in on Creedy's residence, their conversation is masked by Beethoven's 5th Symphony — the viewers only hear the first bar but, when interpreted as Morse Code, it's the letter V (...-).
The graphic novel has Helen Heyer on the other side.
Memetic Mutation: Like you wouldn't believe. From a single Epic Fail Guy comic to the face of worldwide protests. Today, V is the face of Anonymous. Along with the infamous "V" speech. Evidently, Moore is actually quite proud of this fact, but is a little annoyed that it was sparked not so much by his comic as by "the rubbish movie".
Misaimed Fandom: Meta-example, as it did this to Guy Fawkes. It's true that Fawkes entered Parliament with honest intentions, but few actually know what those intentions were. He wasn't trying to take down an authoritarian government, but instill a different one. He wanted England to move from the Church of England, which was oppressing to the Catholic Church, back to the Catholic Church (which would then have oppressed the Church of England).
One could also argue that people who've only seen the movie - which portrays V much more sympathetically and makes the whole moral dilemma much more black and white - are a Misaimed Fandom for the original intentions of the graphic novel, but YMMV.
Particularly since the movie helped turn the iconic Guy Fawkes mask into a populist symbol, frequently worn by protestors at recent events like Project Chanology and Occupy Wall Street. Very few protestors who have donned the mask know that V was actually a morally ambiguous anarchist in the book.
The movie has spread the misconception that November 5th, Guy Fawkes Day, celebrates Guy Fawkes, the plucky rebel, instead of celebrating the fact that England narrowly averted a terrorist attack on the capital. It's like thinking September 11th is an American holiday honoring Osama Bin Laden.
Rooting for the Empire: Happens to V himself, thanks to being portrayed as a saint in comparison to the Norsefire government.
They Wasted A Perfectly Good Line Art: It was originally released in black and white, and then recolored by a different person. With watercolors. In quasi-impressionistic colors. Without paying attention to the lines.
Unfortunate Implications: Frankly, an American-produced movie about the people of Britain willingly electing a politician who's obviously meant to be British!Hitler can be more than a little insulting to British viewers (particularly Londoners) when you consider how many of them probably lost family members to Hitler's bombing campaign in World War II. note Less so for the graphic novel, since it had Norsefire taking over by force rather than being voted in, and the parallels to Hitler weren't quite so anvilicious (the movie renamed the dictator character "Sutler" to make him resemble Hitler more). And, y'know...it was actually written by a Brit.
For that matter, there are also the implications of making the Sutler government a metaphor for the Bush Administration, since the biological attack that prompted their ascension is a rather obvious analogue for 9/11. Said attack (which is widely believed to have been done by "religious extremists" in-universe) turns out to be a False Flag Operation, as a disturbingly large number of people believed 9/11 to be. note Again, this is solely a product of the movie: in the book, the fascists just took advantage of the chaos sparked by a nuclear war to take over the government by force.