From what I heard from people that have read the graphic novel (I bought the darned thing but it got lost in a move and I can't find it so I never got to read it), the ending is different but the plot device is still the same. I think fanboys get bent out of shape when things are different than the originals. Sometimes it seems they forget that its hard to translate everything in to a 2-2.5 hour movie. Some things are just going to get left out.

Just from a pure cinematic standpoint I really enjoyed the movie. I know I'll end up watching it quite a few times. I still want to read the novel, though, just so I can see why people are bent out of shape over the ending.