While I do admit that I did enjoy the film and the change of Ozymandias's master plan was possibly better than in the novel, I do think they went a little TOO over the top in some areas. Specifically, I think they overdid the sex scene and emphasized the violence a little too much. This is one area I think they could've been a little more faithful to the original material with. In the original, Laurie and Dan don't have sex on the couch, as was implied in the film, because Dan was impotent unless he was in costumed and such.
Rorschach's actor were fairly brilliant, too. He certainly has the most stage presence out of the group of actors there, however I think Laurie's actress could've done a little better in her scene on Mars. I'm a bad judge of acting ability, though, so please take that with a grain of salt.
I especially loved some of the details that got added to the film, such as the Silk Spectre poster in the Comedian's apartment, and the porous texture on Rorschach's mask. It's the little things like that which can help you understand characters and such.
I also don't see why people are going nuts about Dr. Manhattan's nudity. I didn't really notice it all that much, but I think I'm just one of those people who isn't bothered by casual nudity in films. Actually, I think it says something that people are more concerned about Dr. Manhattan's penis and not the times Laurie's breasts were onscreen in a far more sexual manner.