Count me in the "pleasantly surprised" crowd. Don't know the comic, relatively low expectations going in, enjoyed the lead actor, art direction, tone.
One problem, though: Smearing. I don't know what the filming technology is (HD video?) but I kept seeing smearing during quick actor movements and generally throughout any live action portion of the movie.
I've seen this in a few other films (notably Michael Mann movies), and I'm very sorry to see it becoming more mainstream.
You're watching a glossy, artfully-directed big-budget blockbuster and then all of a sudden it looks you're watching a 1970s Dr. Who or a soap opera. Distracting, and disappointing.