I really enjoyed this movie. The pacing of the action scenes was well done, unlike LotR where they just go on and on and on... I was a little surprised by all the changes from the book, but in a strange way, they almost make it better. I don't mean to insult any hardcore Tolkien fans, but The Hobbit book feels more like a serial than a cohesive novel, so adding in subplots and LotR tie-ins and other such things make it seem more rounded. I didn't realize that some of the material might have come from other Tolkien works. If that's the case, then I think the fans can rest easy.
All in all, very enjoyable. It's definitely worth seeing.