Personally I'm psyched for it. I think this is something hard to screw up. Even if it doesn't end up being as brilliant as the novel (and it won't), or even coming close, it will still be a kick ass movie.
For length they already said they took out the sort of meta-plot with the pirate in comic book the kid reads, but will be in the directors cut released on disc later (so I hear). And honestly I think they can fit most of it into a movie taking that out. Due to the nature of the graphic novel medium alot of space and time can be taken up having a small conversation or doing a few simple actions that may be a couple pages in the book, but thirty seconds in the movie. Some trimming would be necessary of course, but I don't think they would have to bastardize much of it to make it fit.
It's already got a hell of a script if the actors just sit and recite the comic book, and the visuals will obviously be stunning. So even though I know it won't be as good as the book, I'm still very psyched for seeing it.