Well its still a death explosion thing, there's just no squid involved because the squid itself had too much back story to fit into the movie.
Style/Cinematography was fucking amazing, there was a shot in the opening fight scene that actually made me mumble "that's beautiful" 10/10
Soundtrack was one of the best ones I've heard in years 10/10
Acting, like OP said, some was awesome, some was terrible. Actor who played Dr. Manhattan was horrendous. Rourshank was overall really good but it seemed like the actor prepared by watching the new batman movie for a month, the chick was good, Comedian was excellent. Owlguy was pretty good but nothing special, and there was something about him I didn't really like. 7/10
Plot: I've never really read the whole comic or anything, but it was just a little too esoteric I thought, just for the sake of being esoteric. 7/10
Dialouge was passable but pretty cheesy in parts 6/10
Special effects were epic, but I noticed a clipping issue or two with Dr. Manhattan 9/10.
Overall, it was pretty epic and everything, and it was really good, but it was a little drawn out and the ending wasn't magnificent and it was somehow missing that special something that makes a movie seriously incredible. Fight scenes were really cool and the sex scene was fucking SEXY.
Def worth a watch, I'll probably see it again in theaters, it seems like the kind of movie that might be better the second time. I've never read the comic though, everyone I saw it with that had read the comic was really pissed off.