My issue with the movie was with the ending, but not the change that was made (blaming Dr. M vs having a giant squid) but the decision not to show the piles of bodies in NY. I thought the violence was over the top in parts it didn't need to be (the clever to the head, the cutting off of the guys arms in prison, both weren't in the book) but pussied out in the one part where it needed to be gory. Moore's novel was violent to generate a emotional response and make the "compromise" ending much harder for the reader to swallow. Most people I was with didn't get that "I can't believe this" vibe. Snyder wasn't allowed by the studio to show bodies piled in the streets of NY like the GN, so it was almost as if he was over compensating the rest of the movie. Also, I thought the fighting scenes were bordering on retarded. Part of the idea of the book was that these (except for Manhattan) were normal people who were vigilantes. Why give them super duper strength and fighting ability? I know they were trying to sell tickets, but still, why not have the fighting stay in the realm of normalcy.
It was nice to see the book come to life and snyder stay faithful, but I think on alot of things, he just missed the point.