I didn't like it as much as Batman Begins, but I still liked it. The villains are better in this one. Heath Ledger is a great Joker (no surprise there). Aaron Eckhart is amazing as Harvey Dent. He was my favorite part of the movie. Really great character, good storyline, and I'm happy with how far they took the Two Face transformation. (To all the moms out there that bring their little kids to this movie: Your kids are going to have nightmares. Nice job.)
For some reason, Batman bugged me in this movie.. Particularly his voice. That low, super-gravelly, overly-cheesy voice. It was much worse in this one than in Begins. It sounded like Bale was trying a little too hard to sound like Optimus Prime. It bugged me. And his mask still looks dumb. That's my one big over all complaint about the Batman movies -- the rubbery pointy-nosed mask. Just not very intimidating.
Even though I personally wouldn't place Dark Knight in my "top superhero movies," it's a good flick and worth seeing on the big screen. It'll make bajillions of dollars and I'm sure critics will hail it as a masterpiece.
Oh, and it's really frickin' long. Take a potty break about an hour and a half in or you'll regret it. :P