despite what the ad blitz will have you believe, Zack Snyder is NOT a visionary director. He's a commercial director. He makes films to fill theatres and turn a profit. But it doesnt necessarily mean that he's bad at what he does.
The film, like Rorsach's mask, is a constantly shifting thing. It takes a while to find its feet... and when it clicks, it clicks well. And of course, it was a difficult task up front, condensing the vast and mulit-layered book into a 2 1/2 hour movie. There are times when Zack pulls it off well (Dr. Manhattan's and Roarsach's origins mostly, even if it is layed on a little thick at times), and times when the ball gets dropped completely (Silk Spectre is deflated into nothing more than a talking head, and Ozymandias is a little too cold hearted for his own good). Of course, it could have been better, and it could have been worse. There were some understandable difference between the book and film - some things were taken out that were vital to the point of the book, and there were some additions to the film that were interesting enough.
Watchmen the book is a subtle masterpiece, and deserved better than to be made into a flashy testosterone sex-and-music-and-violence "MTV Movie", but I am glad that it was true to the general spirit of the book, and did not pull too many punches thematicly, and didnt comprimise where it mattered. I would have much rather seen another direct it (a director that is actualy visionary), Oliver Stone or Sam Mendes comes directly to mind. And it would have been better as a 12 part miniseries on HBO than a 2 hour abridged summary. But in the end- It aint the Dark Knight, but it aint Batman and Robin either. And ultimatly, it is worth the price of a movie ticket, and maybe the DVD.