They've certainly managed to capture the look of the comicbook series, that's for sure. I suppose it helps when you've got the artist on the original comics, Dave Gibbons, working with you (one wonders how things would've turned out if Alan Moore was also on board?). So, for the most part, the Watchmen movie looks as close to the comicbook series as a film of moving images and real life actors / locations can look like.
There are differences though. For some reason, they've changed some of the costumes. Rorsharch, Dr Manhattan and the Comedian's costumes and looks are close to the originals. However, Silk Spectre, Nite-Owl and Ozymandias have variations on their comic book looks. To me, Ozy's costume has been changed the most, incorporating more black and less gold, resulting in a costume that doesn't look regal enough. Strangely, they've also changed the shape of the iconic blood splatter. Yes, this is a bit geeky but, still, it is different - albeit more realistic.
It's the story that seems to have been modified the most, from all accounts. Okay, it's difficult to tell from a bunch of trailers, but from various interviews with Zack Snyder and some initial reviews of the movie, it's obvious that some things have changed.
One of the main changes mentioned is, of course, the lack of the Squid. Why they decided to remove the extra-dimensional and psychic creature I'm not entirely sure. It does mean a number of things will have to be changed. The lead up, with reports of artists and writers going missing, is out (supposedly replaced by reports of scientists disappearing). So the link to the Black Freighter comic, which was written by Max Shea and who, in the comic, we saw involved with creating the "alien", is weakened. Also, what did the Comedian see to make him become a target of Ozymandias? He wouldn't have seen the alien on the island and wouldn't have witnessed the genesis of the biggest, cruellest joke on the planet.
The lack of a squid appears to be due to time considerations. I guess explaining to how and the why of this alien being would take up some much-needed time whereas a technological solution (a Manhattan reactor) is easier to explain - even if it doesn't have the horrific impact. Still, apparently a S.Q.U.I.D does appear in the movie. :)
There are probably going to be many more (minor) differences between the graphic novel and the film but, then again, I was kind of expecting that. The fact that the two mediums are vastly different already means that they are not going to be the same and never could be. The couple of reviews I've seen of the movie seem to indicate that, although there are differences, it's faithful to the look, atmosphere and overall story. And that it's a pretty good movie whatever it's origin. That, I think, is the important thing.
So, as Watchmen Week here at PRN starts to draw to a close, there's now only a week to go before the movie is officially out. I'll probably end up seeing it a week or two after that - if I'm lucky. I may even have to wait until it's out on DVD knowing my luck (we'll see).