Saw it Friday evening - and really liked it. I've yet to read the novel, and still might after the movie (read: novel prices) settles.
I think that there was a little too much hype for a film that the general "tanks blowing up, cheesy love story, etc" movie-going audience probably didn't need. I think some people were expecting X-Men uncut with a touch of 300.
Any time a story from a rather lengthy book, graphic novel, series, etc. is taken to film, there is always the issue of excessive source material being fit into one (sometimes more) story that the audience can swallow in a sitting. I think anything shorter than the 2h 45m or whatever, would have been too little time.
Almost everyone I went with was disappointed, for some reason or another. During the movie two guys walked out mid-way through and said, "this movie sucks." I guess it's not for everyone.