Ok, so I will admit that I liked "Watchmen". But, not in a I-don't-understand-what-people-would-find-wrong-with-this sense. I can only speak from my experience of having read the graphic novel a little bit of time before the film was released. The film was an almost-exact carbon copy of the graphic novel...of course with some minor changes and bunching together of scenes to get to the point (like the assassination attempt on Ozymandias, and the missing explanation of Rorshach's mask, and the ending).
My theory is: people at least minutely steeped in the comics world will understand what author Alan Moore through director Zack Snyder (Moore said that he hated the fact that they put his work in Snyder's hands and will never watch the movie himself. I completely understand. "300" was horrible) is trying to portray in "Watchmen" immediately: taking the mythological images of superheroes and placing them in the real world with a very in-depth and gripping narrative. On the other hand, people who have confined their minds to the "real" world and expect to only see things they're familiar with will see the film talk about the Vietnam War, the Cold War, Nixon, and other things, and then see these silly people with colorful costumes showing up with their ridiculous personal problems and intense gore and blood all over the place and wonder what the hell is going on. A co-worker at my job took her kids and husband to see the movie because she thought it was some sort of children's story akin to "The Incredibles". After explaining that the film was very much for adults, she went to see it with her family anyway ("my kids watch violence at home all the time, so why not?"). Of course she didn't like it, which I think stems from the fact that she barely knew what the hell was going on (one of those people that can only attach herself to the simple things in life).
I'm a fanboy, so of course I enjoyed the fact that "Watchmen" was just like its literary counterpart. I thought the acting was superb on all counts. What I find additionally interesting is that, everyone from the people who have just seen the film to those who have just read the comic find Rorshach as the most interesting character. I agree, and I think that Jackie Earle Haley translated him on to the big screen perfectly. The opening montage was probably the best part of the whole film. I enjoyed the martial arts that Snyder worked into the story. The graphic novel hardly has any action of that kind in it, but bringing a story about superheroes into film would also breed some expectation for fighting in the public's eye (unless the film is advertised otherwise). However, the computer graphics in many parts of the movie were downright awful. Especially notable were the scenes that took place in Antartica and views of New York City from above during the ending, which looked like the director had a 10-year-old designing it.
So, overall, I'm not going to just up and recommend the film to everyone, but I'll say that you should read about it and a little of it's history and rapport with it's pre-established fanbase prior to viewing. It's not a typical story, and I'm not really sure that Snyder did a good job of introducing it to newcomers. I will definitely recommend that everyone purchase and read the graphic novel though, especially if you're a literary person. You can read my take on this here.