Overall I liked the film, there were just a couple things that bothered me. Overall, Batman wasn't nearly as much fun to watch as the first film. There was no real movement in his character, he just got a new suit with a new set of toys. The rest of the good guys were pretty static as well. Rachel, Gordon and Alfred towed their standard lines, while Two Face was disposed of too quickly after using so much of the film to develop his character.
Now that said, The Joker was absolutely brilliant. I haven't seen a performance like that since Marlin Brando in "A Streetcar Named Desire". In one way it makes his passing even more troublesome, but in another it makes it tolerable - is acting was genius, most actors never achieve what he did in that role and maybe that stands as some small consolation.
Ledger's performance aside, Wall-E struck me as the better of the two films (if I were forced to make a comparison). Where I would make no adjustments to the plot or presentation of Wall-e, the Dark Night leaves me less satisfied.