Last night we got to see The Dark Knight a few hours early courtesy of some vendors at the conference I'm attending. I enjoyed it immensely. It really was better than your standard summer movie comic book adaptation pablum, and yes, Heath Ledger showed he would have been an amazing actor with a great career.
But the plot can be summed up thusly: The Batmobile lost a wheel* and Joker got away.
*Actually, two wheels, and they became a motorcycle, but close enough.