Saw it twice at home and then in the cinema, entertaining each time. Besides the car chase scene (which fucking sucked in both movies. STOP with the one-liners for the love of God) there was nothing in particular that I disliked. The philosophy was pretty basic but the theme/dialogues were still interesting. Had the script been a bit better it would've been one of the best movies I've seen in the past years but it's the best comic book movie by far. The set-up was perfect but the execution was not without its flaws. Some people said it was too long but I think they could've made some scenes stronger had they added another 30-60 minutes.
Heath Ledger was fucking great. I've seen him in plenty of other roles and I could've never imagined he'd be able to pull that off. Jack Nicholson played the roll well but Heath took it to a whole nother level. They took all the important elements from The Joker, especially his relationship with Batman, but put the perfect spin on it. Definitely the most interesting comic book villain ever portrayed in film.
Really looking forward to the third one and very curious about what villain they'll take. Maybe Poison Ivy and it'll be a psychological journey into the mind of a hippie.