I don't really know about acting, and I don't know the names of actors, but Heath Ledger as The Joker was brilliant.
This was a morally complex batman film. I saw it as an allegory of the 'war on terror' / war in Iraq, with The Joker as Osama Bin Laden and Batman as the US military.
The issue of torture arose, in the classic situation of a person refusing to say where the ticking bomb is. Batman resorted to torture, like water-boarding carried out by the US. I listened to The Moral Maze on torture, and was horrified to find myself agreeing that it was right to use it in certain circumstances. I can't remember the reasoning and if someone asked me now, I'd say torture is never justified.
Another part of the war on terror is surveillance. In The Dark Knight, batman hacks into everyone's mobile phone and builds up a sonar picture of the city.
Even the cold war comes into this film! In an analogy of the cold war, each ship can destroy the other at the touch of a button. To have the best chance of surviving, it's rational to press the button straight away.
Fate has ordained that the problem of free will occupy my mind. Batman has to choose between saving the life of the woman he loves, or the life of the man he believes can save the city from crime. Is his choice determined from the beginning of the universe, and even if not, does he have any real control over his choice?
It's a great film, but for me the moral choices are clear. Batman shouldn't go around breaking the law, he should respect it like any other citizen, no exceptions. Equally, the UK / US shouldn't have undertaken an illegal war against Iraq.