I have about seventy-million little things to say about this movie. I will try, and probably fail, to keep this brief.
Spoilers definitely ahead:
The movie is really, really good. It's not flawless, but it covers it's flaws through a very strong sense of what Batman means and doesn't mean as a character, and also because it's very intense. The movie spends most of the time feeling like its on the very edge of chaos and conflagration -- it's probably the first time that I've genuinely felt that the hero wouldn't "win" in superhero movie.
Heath Ledger is getting a lot of praise, and deservedly so, he's outstanding. I'm also interested in how the movie manages to capture the icon of The Joker while using almost nothing from the canonical comic version. (Early on, Gordon or somebody calls The Joker just a guy in makeup and I thought, okay, nobody knows that's what he really looks like. But in this movie, he is just a guy in makeup.)
The comic version is, at least recently, usually shown as already the head of a large empire, and also usually as having a plan. In Alan Moore's Killing Joke, which is probably one of the main comic book influences on this movie, The Joker plans to destroy Gordon by giving him the worst day of his life. In this movie, the idea to destroy Harvey Dent is more of a target of opportunity. The movie Joker doesn't really plan -- he's the anti-plan, just chaos. And the movie doesn't flinch at showing how scary that can be with very little effort.
Often, superhero movie series come to feel like the hero's greatest hits album -- a series of unrelated stories. One thing Dark Knight is very smart about is exactly how The Joker arises in direct response to Batman disrupting Gotham's mob scene in the first movie.
I really never thought I'd see a Batman movie go all the way to, "Is Gotham really better off with Batman there". It's a common feature of superhero sequels to have the hero struggle with giving up the fight. But in Superman 2 and Spiderman 2, the hero is trying to decide whether they can be personally fulfilled while being the hero. Batman is beyond that, in Dark Knight he's trying to decide if he's done any good at all.
Which brings us to Harvey Dent and Two-Face. Who, interestingly, is much closer to the comic version (although in the comic version, the Dent defaces the coin himself after he's injured -- actually, the movie version is better...) I really like how they kept contrasting what Batman could and couldn't do in the shadows with what Dent, as DA could and couldn't do in the public eye, and how Batman was almost eager to have Dent be Gotham's by-the-book hero.
The sequence where Rachel dies was a bit odd. My read on it was that the Joker didn't really care which one Batman tried to save, he just wanted to make sure that he'd fail no matter what. Still, it seemed out of character that Bats would go after Rachel.
The movie's use of the Chicago locations is outstanding. (Frankly, everytime I'm on Lower Wacker, I always kind of feel like I'm in a creepy action movie). Despite the fact that Gotham is nominally fictional, the locations ground it in a way that say, the Spidey movies don't quite get even though they use New York as itself. Or maybe that's just because I'm more familiar with the Chicago streets used.
One question that I keep wondering about is whether these two movies would have been successful 20 years ago in place of the Burton movies. Assuming, of course, that the studio in 1989 would have let that movie be made. I'm not sure. I know the fan base would have still loved it.
Also. Is it the best superhero movie ever? Right now, I make the top four, in no particular order, as Spidey 2, Dark Knight, Iron Man, and The Incredibles. There's another story about how the movie that would have been considered as the best for years and years (Superman 2) has had it's critical stock bottom out recently. I'm not sure on the order of my top four, though..
I'll probably think of a dozen things after I post this, but that's all for now.