Loved it. A really taut sci-fi thriller; it really did keep me on the edge of my seat. I liked the characters - no one who was too stupid to live, lived, which is not usual for many of the movies I see - and the pacing was expert.
The creatures were - interestingly designed; I think they should have made at least one change to them, but maybe I'm just sensitive. The ending was a little weird, but I definitely didn't see it coming, so hey, props.
Definitely worth the matinee price.