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.
The book was a famous bestseller in its day and indeed in its year of publication(in the 1920s) created a wave of interest in what was, even then, a bygone era and was highly regarded by the likes of Jorge Luis Borges. Scorsese had wanted to adapt it since the 1970s.
Out of the 5 actors nominated for the Best Actor Oscar that year, Daniel Day-Lewis was the one who received the most prior awards for his performance, winning several awards (including the BAFTA and the SAG). Coming into Oscar night, Day-Lewis was the likely favorite, and yet he didn't win.
Awesome Ego: There are two occasions when Bill responds to a cheering crowd with a dismissive, even bored, royal wave. Rather than coming off as pretentious or pompous, his arrogance comes across as so totally justified that the moments appear on the Moment Of Awesome page.
I thought that was just another one of the many examples of hellish symbolism that crop up throughout the film. Attention is repeatedly drawn to bits of scenery or striking imagery that make it seem like the Five Points are Hell (young Amsterdam being sent to "Hellgate" school and eventually passing through it and returning to the Five Points after throwing away his Bible, the devil puppet with "Satan's Circus" written underneath it, Bill arriving on a fire truck that seems to be pouring red smoke before taking his place on a makeshift "throne" surrounded by fire and fighting etc.), and the silhouettes cavorting in front of an inferno seemed to be part of that.
Draco In APimping Top-Hat: Bill Cutting. Not that anyone else in the movie is a good person, but for some reason Bill gets lionized above others due to his Badass factor.
Harsher in Hindsight: A lot of the anti-immigrant viewpoints of Bill's gang and the Know-Nothing Party are eerily similar to anti-immigration rhetoric in America today.
Nothing new under the sun. America has gone through repeated periods of anti-immigration extremism. Usually the previous major immigrant group is at the forefront of opposing the newcomers.
Hilarious in Hindsight: Daniel Day-Lewis played Abraham Lincoln in Lincoln. Extremely hilarious when you think about Bill the Butcher shouting "Down with the Union!" during a performance of Uncle Tom's Cabin and throwing a knife through a picture of Lincoln earlier in the film. Made even funnier with the fact Day-Lewis was nominated for Best Actor Oscars for both roles and won with Lincoln instead of Gangs.
Also, Bill's rival in this movie was played by Liam Neeson, who not only was the original choice for the role of Lincoln, but gave a notorious Take That against Day-Lewis and his Method Actor style in an interview, claiming that he could rely on his own acting talent for a role and didn't need to "live like the part" the way Day-Lewis is famous for.
The plot of the movie could easily be described as Kill Bill.
Even better: the DVD includes a trailer for that movie.
Particularly remarkable because Bill does not display the flawless complex planning or subtle manipulation that are normally associated with magnificent bastards. In fact, it is quite clear that he knows he's fighting a losing battle, and will go down fighting anyway for his principles, but is also a hypocrite with some of those same principles. Despite these significant failings, he is such an electrifyingly charismatic character that he manages to inspire awe rather than disgust. All kudos to Daniel Day-Lewis for managing to pull this off so gloriously.
Lawful Evil: Bill. He follows his own code and is definitely the guy in charge in the five points. He believes wholeheartedly in the rule of law, albeit his own.