I'm not 100% sure about specifics but when any of Alan Moore's comics get turned into movies they end up heavily rewritten and the dialogue, which normally is filled with panic and confusion, is rewritten in a way that is "worthy" of an epic hollywood movie. I.E. in the commercial Dr. Manhattan asks why he would save a world he no longer has any stake in...and the girl's looking all cool and calm as she says "do it for me." In the comic, she was pretty much hysterical. They're also supposed to be changing how the ending happens. Watchmen could still be a great movie, though. Take V for Vendetta for example. Same author, totally rewritten. Not very true to the source material, but still turned out to be a great movie.