When I watched the movie the first time I was disappointed and thought it was a mess, but I was a HUGE fan of the book. Essentially, the movie wasn't the movie I wanted it to be. Since then I have watched snippets of Gangs of New York when it was playing on Showtime, et. alia, and always liked what I saw. You have convinced me that I should rewatch it.
I was talking about Gangs of New York two or three days ago. The book has a long discussion about the different police forces in New York at the time. Policing, it turns out, has a history as complicated, dark, and mythologized as the rest of life.
What a great post.