Well...
Hurm.
I liked it. I did. It was an enjoyable cinematic experience, and I recognize that I have trouble objectively reviewing it as a fan of the comic. But it never wowed me. Maybe this was a little much to ask, but it was never as awe-inspiring or as emotionally real as the graphic novel. There were certain scenes that did make me very happy: The opening credits, Dr. Manhattan's monologue on time, the sex scenes, Rorschach defending himself against his fellow prisoners. But all in all? It never quite captured what made Watchmen so powerful: that the entire time, it felt like the writer was telling you the truth. Zach Snydyer did not make a truthful movie; he made one that was fun to watch. It never means as much.
I was also not too pleased with the cuts that happened to Ozymandias. I know he's never been exactly a fan favorite, but he really deserved more. His "Alexander the Great" monologue was cut so much that it was almost unrecognizable, and he never got his "I did it!" moment after his plan worked out. Maybe I'm off-base, but I think that keeping in those scenes would have been a benefit to the character.
And I can't help but contrast the endings of the novel and the film. The ending in the novel nearly made me weep: Rorschach dying without anyone there to mourn him, Dan and Laurie having their last love scene by the pool, and Dr. Manhattan giving one last ominous warning to Ozymandias. In the film, we get Rorschach's death, but the Dan-Laurie scene (probably one of the best in the book) is cut entirely, and Dr. Manhattan just... leaves.
Maybe I'm being too demanding. But it seems to me like it could have been so much more.
But one more thing:
BEST. SEX SCENE. EVER.