Just saw it at IMAX, and as a fan of Frank Miller's original work, I must say that I wasn't disappointed. The movie's faithfulness to the original is commendable. Even if you didn't like it, you have to admit there could have been LOTS of things, if done differently, that would've made it horribly bad. I shudder to imagine what a director like Uwe Boll would have done with this movie. As it is, the tone of the entire movie is spot-on with Miller's original.
One of my friends, also a big fan of Frank Miller, told me that he was smiling to himself so hard throughout the movie that his face hurt. While mine doesn't, I did find myself grinning for most of the movie.