Saw it on Thursday night (opening night in the UK) and yes, I do think Heath Ledger did an amazing job as the joker. Beats the hell out of Jack Nicholson's turn, but it has to be said, he wasn't the only villain in this piece.
Two-face was, I think, incredibly well done. (From a visual standpoint alone, I'm amazed this film scraped a 12A). We're not talking a Tommy Lee Jones (sort of) slight disfigurement in this film. The two face effects were awesome, effective and really quite grisly. In a packed cinema (and I mean, there was barely an empty seat in the place) his first reveal produced a very audible simultaneous intake of breath from damn-near everybody in the place, and Aaron Eckhart did a fantastic job of really making you feel for Harvey dent.
All-in-all though, I have to say that as a comic-book movie, it plays second-fiddle to Iron Man as '2008's Must See'. I enjoyed it immensely, but I don't remember feeling so exhausted walking out of any other film I've watched in a long, long time. Iron man left me walking out on a high, hungry for more and arms-open for a sequel. The Dark Knight, not so much. If only because I'm fairly certain Christopher Nolan won't return for a third chapter, and in the hands of anybody else, Who knows how it it'll tun out?