Out of nowhere, but I've been lurking, and this is my argument for the film.
Ever since the beginning of what I always thought of as the Big Rush of comic book movies (Batman Begins, all of the Marvel films, etc.) One thing I've tried to do is think about the films in the context of the medium. What works in one medium does not necessarily work in another. For Example, blue Hair looks cool in anime, yet never seems to work as well in real life. So too do certain conventions of a comic book fall flat when you try to take them off the page. Most of the comic book movies from the past ten years have been pushing and pulling on the notion of what actually "can" be, in a sense. Granted, a lot of comics are trying to do that now. There's a pull for making the non-sensical a little more grounded. This isn't the 50s when saying "The Far East" evoked an unreachable land of mysticism and magic, allowing writers to tell American children anything and it's believable (One reason why Alan Scott found his lantern in the Far East, and Hal Jordan received his from space).
I look at the Christopher Nolan Batman films as an interpretation of "What if this actually happened?" Some of the villains don't quite call themselves by their comic book persona. There's not colorful costumes, except the Joker, and that's just a custom suit. I custom suit I ant very badly, but I digress. The main problem is organized crime, the "Batman Villains" are just major elements of that same problem.
That may not be exactly what you read in the comic books, but the comic books aren't always what you read in comic books. There have been so many writers, and so many restrictions (like the comics code authority) that any character that's been around for a few decades is going to have a sort of margin of interpretation, from which you pull what you believe to be the "definitive". Hell, the Joker's been around long enough that we can debate interpretation in live action, and animated portrayals as well. In the situation of a 68 year old character, definitive is in the eye of the beholder.
My take? I loved the Dark Knight. I felt it went beyond the feeling of a Comic book movie, and stands on its own, without needing to apologize for itself because of the medium it sprang from. I interpreted Batman Begins as being about Fear (obvious yes, but still). Obstacles were to be pushed through, similar to how you face your fears. The Dark Knight was about illusions. I say illusions of the magical variety. The obstacles of the film had to be seen through, rather than pushed through, to be overcome. The Joker was a street magician in a sense. He pulled little tricks, he conned his audience, he fit his patter to his victim. Harvey gave the illusion of luck and fairness in one way while playing the hero, and another after his accident (which I felt was a believable explanation, in a fashion). Also, it struck me that the imagery of the two rogues of The Dark Knight were cards and coins, two staples of close-up magic.
In conclusion, "In all the old familiar places" (my favorite line from the film, think about it.)