The movie as a whole was decent, as Zach Snyder was nice enough to transpose most of the book verbatim to film. That said, any intelligent discussion of morality or clever analysis of superhero literature was entirely Mr. Moore's, and nothing Zach Snyder added to it was really all that clever. I felt like he kind of half-assed it. All he contributed to the story were these little sophomoric touches like skanking up Silk Spectre II's costume a bit (which was a little out of character) and cranking the violence up to retarded Frank Miller levels, which has to be insulting for a clever writer like Moore. Most of why I liked this movie had to do with the cinematography and the casting.
He directed the rape scene as though it was a vaudeville comedy piece, and filled it with his characteristic earth-moving punches. Everything was so exaggerated. Comedian throws SSI into the ****ing pool table so hard it moves, instead of pinning her to the ground, which was a lot more ominous in the book. She scratches him in the face lightly, and he loses it, but Snyder has to turn up the violence knob and transform a scratch into a ****ing right hook. The inclusion of the punch over the scratch makes the scene look like superhero foreplay, and not an attempted rape. He also cranks up the violence to satirical level during the Comedian's death. The first time I saw a brick wall get punched through, I laughed my head off. The sex scene in the owlship was also terrible. He turned a very human moment in the book into late night skinemax.
Things Snyder got right? I though the way he treated Doctor Manhattan's origin was pretty moving.
So, in short, the movie succeeds in places where Snyder doesn't mess around with things, like Doc Manhattan's chapter, and fails where he does, like the rape of Silk Spectre.