I'm a little late out of the blocks on this one, so I'll keep it short. This is one of the films that managed to catch me up as a screenwriter and scare the pants off me. And it does it while largely centering on some fairly heady thematics about the nature of a hero in a society governed by random acts and raw power, an effective response to nihilism, America's deepening fear that it's about to eat itself, and, well... I'll stop now. The film searches for meaning in a way that few indie films dare without diminishing the blockbuster impact in the slightest. If you've got a budget of $185M, you can do both! It seems there are more and more big movies willing to mean something these days. It's a very good thing.
I'm overcoming my kneejerk reaction to John Truby here and linking to his post on The Dark Knight. I'd post a spoiler alert, but I think everybody's seen the movie anyway..
Check out Truby's article in Storylink.