I am surprised to read that so many people think that this is a fabulous masterpiece. It is better than most superhero films, but that isn't saying much. Christian Bale is quite bland as Bruce Wayne, and a bit over the top as Batman. The film never gets to grips with how he behaves as Bruce Wayne, either in public or in private. It is interesting that he is never shown enjoying his wealth, but nothing much is made of this.
Whereas "Batman Begins" was good in that it went to some trouble to explain how Batman could get hold of his astonishingly high-tech gadgets and vehicles, in this film we are required to believe that he makes some stupendous gadgets himself, very quickly, using his development company, but without its knowing. There are some rather improbable rooms that such things happen in, too. Be realistic or be stylised and fantastic - make your mind up. Similarly, decide whether Batman is a human, with the abilities of a human, or some super-human, but this film keeps trying to have it both ways.
Heath Ledger is indeed good as The Joker, although really any actor worth his salt should have been pretty good in this gift of a role.
The casting of the love interest was bizarre. We have to believe that Gotham's two most eligible bachelors are both dotty over her, and the dialogue keeps saying that she is amazingly beautiful, but the actress cast is fairly ordinary-looking, and the script writers never give her anything to do or say to make her adorable.
One major criticism I have of the film is that Gotham City, which we are told is forever poisoned by corruption, looks so nice. The buildings are all well built and maintained. The streets are sunny, well laid out and litter-free. The city is clearly prosperous and well-run. There are several hospitals, all clean and with good equipment. Whenever the city has to organise anything, all the various employees of the city spring into action efficiently and things happen, again and again.
The next big criticism is that the film is FAR too long. It appears to come to conclusion, and then keeps going, with twist after twist, each more improbable than the last. Whereas the film works pretty well as thriller for the first half, the endings strain credulity and patience. The Joker is able to place bomb after bomb in all the right places without anyone's suspecting, and the police's actions get more and more stupid.