Really, the movie doesn't even have that much of a plot. The story is pretty typical superhero stuff and has no real details. The first movie had much more. Still, I enjoy this one for what it does have. I do agree that I didn't buy Dent, though. I thought that was somewhat mishandled (though it stung less on third viewing), and even beyond that it was a mistake to kill him off so quickly.
The movie may not be a masterpiece, but it does at least continue the legacy of the first movie from the perspective of a suitably dark Batman and a truly adult, serious superhero epic. Next outing (if there is one) they really just need more of a story. This one was basically just "guy in bat suit fights mental patient in clown suit". Great characters, but not much intrigue.