The first part of the film is pretty poorly edited, but what takes the cake is the fundraiser scene.
SPOILERS FOLLOW, of course.
The Joker shows up and Bruce Wayne puts Dent in a closet with a broom handle holding it shut (he'll NEVER be found there!). He confronts the Joker and the Joker tosses Rachel out the window - Batman leaps after her.
And?...
The Joker is still at the party, right? Batman's no longer there to stop him from achieving what he came for - to find and kill Harvey Dent. So why didn't he? There is no acknowledgement whatsoever of this nor any explanation of what the Joker did at the party once Batman left. Did he kill everyone? Why didn't he find Dent? Did he just leave? If so, why - when he wasn't finished what he came for and Batman was safely out of the way?