Whenever I go to see a movie that adapts a character/characters or a book to the big screen, I hope that the essence of the character or book is captured in the movie. When you adapt something to the big screen, there are always going to be changes, modifications and such, because of the difference between the storytelling in books and comics and movies, however slightly one might think of the differences. The first "Spider-Man" film, for example, captured the essence of that character very well, though the movie wasn't a complete literal translation of the comic book character.
I saw the movie Thursday night with my girlfriend. I thought the "Watchmen" movie captured the essence of the graphic novel. I enjoyed the film, thought the acting was well-done, the story coherent, and the visual experience arresting, at times.
I tried to watch it with two sets of eyes-- one set seeing how well it adapted the novel, the other set trying to see it as someone who never read the novel. My girlfriend is someone who had never read the novel. I asked her afterwards if she enjoyed it, was able to follow the story, were there any plot holes, questions of that nature. She told me she liked it a lot and was able to follow the story, explaining to me what it was about, demostrating that she was able to follow it. We did this as the credits rolled. When I like a movie, I stay in the theater until the credits and such run out, to show my appreciation of the effort the filmmakers made. This is an unseen appreciation, to be sure, for the filmmakers will never know I was there until the very, very end of the movie.
So, based on our viewpoints, I think "Watchmen" accomplished that rare feat of pleasing both types of audiences: readers and non-readers of the graphic novel.
The secondary effect of how well the movie was done: I want to read "Watchmen" again.
The desired secondary effect of the creators, financers and distributors of the film: I want to see it again.
The wishful effect for the secondary market for the film: I can't wait for it to come out on DVD (I'm not a Blue-Ray'er at this time).
Now if DC can fix Superman and Batman....