I remember talking to a co-worker about V for Vendetta and saying that while my husband and I liked the movie and didn't mind the changes, the graphic novel was darker, and the friend gaping at me as if I had spoken in Aramaic--how could it be darker.
The fear is, of course, that Watchmen will not be dark enough, and my own personal fear that if it is dark enough, it will not be what most of the audience is expecting. As in this early review (it's out in Britain):
He seems angry that they aren't really "Super" for super heroes. Well, neither are Batman and Iron Man if you mean super powers and not just really good toys, lots of money and brains. What the 80's brought in comics was a realization that it was much more interesting to study the superheroes rather than just their crimes. In a way this reflected the general trend in "escapist" entertainment. Hill Street Blues was much more about the tensions in the police HQ than the crimes, and the particular tensions of being a cop were what made the show great.
Likewise, the study of the particular tensions of costumed super heroeness has become rich ground. Even Superman gets angst these days.
This reviewer seems to get it (warning--major spoilers):
What happens when you are not needed? What happens when you become a God? Are costumed heroes really just sadistic vigilantes? Are they any better than mercenaries?
Moore's deep cynicism is part and parcel of Watchmen, and I'm not sure that an audience that likes it's comic book adaptions to have a romance a la Peter Parker and MJ, and a happy ending is ready for him. Certainly V for Vendetta suffered from that, but had Natalie Portman's star power. Watchmen, with the exception of Billy Crudup (who spends much of the movie as voice talent to a CGI version) this seems populated with B-listers.
Likewise, dark as Nolan's Batman films have been, the love story and to a certain extent the surrogate fathers of Alfred and Morgan Freeman's Lucius Fox give a sweet anchor to the fact that Bats and the Joker are much more alike than unalike. Here the villains are awfully close to the heroes or vice-a-versa--and that is much more like real life.