Zach Snyder is who we thought he was.
He attacked the movie with admirable fan boy zeal, but he lacks so much any artful romance that you wonder if his proposal to his wife didn't involve mostly martial arts. The set pieces were fantastic, and the tasteful opening scene was done by someone you can tell just thinks in comic book format, but the movie did come across as a book on tape at times.
He had to make some tough decisions when filming a book explicitly designed to be unfilmable. For the most part he succeeds. His additions and subtractions are all necessary (almost), as sad as it is to lose the newspaper vendor as narration (although both he and the comic book kid make a predictible and notable appearance towards the end). Some changes snowball into other changes that seem completely arbitrary, even though they aren't (hint: Dan Dreiburg isn't blonde and in hiding in the end). These are the things you deal with in exchange for seeing these guys in living color.
The biggest thing he failed to do was use music in the movie in a way even approaching competently. Comic books are silent, so he had free reign to do what he wanted. Alan Moore Dave Gibbons should've slapped him stupid before they let it get that far.
There were three crucial things that Snyder had to hit in order to make a successful movie: the casting, the Dr. Manhattan exodus scene, and the ending.
The cast had the herculean task of playing actual cartoons without making them appear as silly as they most certainly would be. For the most part they succeed:
Rorschach: A+. Nailed it. Easy part to play, but nailed it.
Dr. Manhattan: B. Billy Crudup is a good actor, but he had maybe 5 minutes of screen time as a human. The rest of the time he was voicing a big rubber lightbulb, trying to sound as inauthentic as possible. He succeeds, I guess. He's one of many people that suffers from the sub-par direction of a man who, as I can only assume, has never seen human interaction before. In this case it works.
Dr. Manhattan's penis: F. I realize some men are shrinkers and some men simply turn off, light a light switch. Sweet merciful crap, couldn't you have made him a shrinker!?
Nite Owl: A. The most vulnerable character gets a nice treatment. Finally, a superhero with a body like mine!
Silk Specter I/II: F. You know how in basketball, when the other team has a really good player who will score through double teams anyway so you just choose to let them go off on you while you defend the rest of the team and hope the star can't beat you on his own? Basically, you throw your hands in the air, give up, and don't even try to deal with him. In this scenario, Alan Moore's long, awkward monologues would be Kobe Bryant, and Malin Akerman would be the scrub assigned to guard him. But she's dynamite in bed, or at least good enough for Snyder to risk ruining his movie for her.
Carla Guigino goes the caricature route, unfortunately. Acting is not in the Jupiter genes.
Richard Nixon: D. Gets way more screen time than is necessary, and doesn't earn even an iota of it. This would be an easy F, but I am grading on a curve. Following an Oscar worthy creation of the man in Frost/Nixon is unenviable.
Adrien Veidt: B-. Actually a nice job, despite casting a teenage girl. I never read Veidt as having an accent, but whatever. They did. Wasn't awful, I admit. It was probably the hardest part to play, and Matthew Goode manages it, veteren QB style. Nothing flashy, you know?
Dork Humor: A+. I always enjoy it. The McLoughlin group at the beginning of the movie pulls a line right from Dana Carvey's depiction of the venerable host. Only I laughed audibly.
The Comedian: C+. Looks just like you'd expect, but Zach Snyder's direction must've been something like "I don't know, just read it. (to aid) We need more karate chopping!"
The guy was a bastard, but they might as well have given him a mustache and cape. Nyahh!
The Dr. Manhattan chapter is important to only me. I wanted them to do it right. Without speech bubbles and the meandering writing style that a lack of a time limit can create, it doesn't have the same gravity that the book did. But they executed it perfectly well, like the final montage in a season of The Wire. I would've preferred they treat this scene with a little more respect and take their time, but what can you do? I'm just a dork on the internet.
Now, the real stuff. The changes. Nerds are artistically autistic, in the sense that once they create their world you had better not change anything, unless you want to see a tantrum. I will try to balance my soapbox outrage with respect for spoilers.
First, the news vendor and comic book thread is gone, save from a cameo. This is understandable, as it would add another 90 minutes to the movie.
Hollis Mason survives! I am happy for him, although that scene was pretty important, however small.
The prison psychologist's back story is gone. Fine with that one.
Because of the plot consolidation, a lot of dialogue is moved around, to no great consequence. For instance, Dr. Manhattan enjoys the uncertainty he hasn't felt in decades in Veidt's fortress instead of NYC, post disaster. Whatever.
Veidt's incredible murdering of his servants is gone, understandably. It would've ground the movie to a halt at the climax. But man, what a shame to lose that.
Dan Dreiburg is there for Rorschach's finale. Why? Fuck if I know.
Overall, considering the difficulty, I was actually pretty impressed with how they put together the story. Except for
The ending. F-. F- - - - -. The squid, motherfucker. Where is the fucking squid!? Why! Why why why did you cut the damn squid!? So you didn't have to spend 5 minutes of movie on the island? Congratulations, idiot, you messed with one of the 10 best literary endings in the history of the world for no discernible reason. I won't even say what they replaced it with, because I am so disgusted. I will only see this movie 7 more times.
Watchmen: F-. Worst. Movie. Ever.