The first Watchmen trailer aired before The Dark Knight, and I was more excited than I was apprehensive. (This might have something to do with the rather good Smashing Pumpkins song it was paired with - “The Beginning is the End is the Beginning” - which was both lyrically appropriate and had the added bonus - and liability - of being used in a previous superhero movie. But I think that was the point - more on that later.) From what I can see, there are at least four obvious aesthetic touchstones in play: the source material itself (Zack Snyder has lifted several of the trailer shots directly from Dave Gibbons), Frank Miller film adaptations (both Snyder's own 300 and Sin City), the Burton-Schumacher Batman films (though the color and contrast, and the Pumpkins song, are more suggestive of the latter than the former), and Dark City (the Rorschach scenes and comparatively drab and washed-out urban backdrops seem to suggest this source). Drawing these connections seems doubly important because Snyder has apparently claimed that just as Watchmen consciously draws on the history of the superhero tradition in order to revise and reimagine it, he plans on reappraising the superhero film genre.
All that said, it's difficult to judge whether the film is actually any good based on the trailer. Rorschach looks exactly like he does in the comic and Jackie Earle Haley seems like a good choice, just as Jeffrey Dean Morgan strikes me as perfect for the Comedian; Billy Crudup and Matthew Goode I'm not so keen on, especially the latter, though I'm willing to wait and see. (Were budget not an issue, Ozymandias would seem like the perfect role for an aging pretty-boy star - like Tom Cruise or Brad Pitt - or perhaps a former star on a career downturn, preferably someone who's played a superhero before like Michael Keaton or Val Kilmer.) The importance of Dr. Manhattan's visual presentation to the success of the adaptation probably can't be overstated - if it doesn't look 'right' (and who's to know what will look 'right' until we see it?), it'll be nothing but a distraction. Though I think, for instance, that this one looks pretty cool:
One last thing: apparently, there was some sort of youtube contest connected to the film where people were encouraged to make their own in-story commercials for a Veidt (Ozymandias' company) corporate product. I haven't looked at many, but this one is hilarious in its perfect reproduction of 80s toy ads: