There are simply too many unanswered questions to make this movie enjoyable. Little things like, why did they come here? What happened to the ship to make them stay? Why didn't the humans dissasemble the ship or maybe even post a guard or two?
I also dislike intensely the jerky camera movements (must've been the same camera man as the Jason Bourne series).
CGI was awesome, acting was quite good, plot was ok. If you can deal with unanswered questions then you would probably enjoy it. The format (interview style) was interesting, but it eventually leads to trouble when they try to tell the story (i.e., I was watching an interview a few seconds ago, but this scene cannot be, whoops, I'm back to an interview scene, etc.).
Seen all of the Potter movies and this was the slowest moving one. It was just ok. Some disappointing events but they are spoilers. Kind of hard to follow for someone who hasn't read the book, I guess.