In terms of action, I think the movie was good and fast paced (as it should be). The mood was dark, the plot twisted (in a good way), and it was overall well done, especially with the visuals and special effects. Gotham came to life as a corrupt, two-faced city, as it did in Batman Begins.
Heath Ledger's performance as the Joker was good, but not quite as good as the hype made it out to be. The Joker is a man who is intelligent, twisted, maniacal, greedy, and pitiable. I think Ledger came close to delivering all those qualities to meet my expectations, but somehow I think he fell short in displaying that sheer jocular-maniacal quality that is distinctively the Joker. I think the Joker from "Batman: The Animated Series" is the best incarnation of the Joker, but perhaps that is because animation allows for exaggerated facial expressions that are simply not possible in real life (the creepy voice acting done by Mark Hamill was superb, too).
Michael Caine was fine as Alfred, though he seems to offer too much sage advice - he shouldn't talk as much, in my opinion. Maggie Gyllenhaal as Rachel didn't add much to the movie, or take away much, so I won't say anything about her. I think Gary Oldman was the perfect Gordon, though, and Aaron Eckhart was good as Harvey Dent. The Two-Face story should have been fleshed out in a different movie, however.
I don't find too much to complain about Batman himself (Christian Bale), but I do agree that the raspy voice is a little annoying. If his voice were simply deeper, and not raspy, I think it would have come out better. To me, it always seemed as Bruce Wayne was the false identity, the one with a fake voice and personality, and Batman was the true. Bale did stay true to that in his acting, but in "Batman Begins" and "The Dark Knight", it seems as Bale is hurting his throat trying to talk like that. It's not that big a deal, and the effect is still plausible, but I am saying it could have been done better (maybe not by Bale, though).
"The Dark Knight" was a good movie, but not "the best movie ever" (many of my friends disagree with me). It was the best superhero movie I have seen, though, and was a good enough adaptation that it didn't make me cringe at various parts throughout the movie - a rare thing for any movie of this genre ("Iron Man" is the only other exception). It was also a sequel that greatly improved upon the original, and that, too, is rare.
9/10 rating for "The Dark Knight"