Climbers vs Crawlers. I really dug this movie, but the insta-crush I developed on the original Juno, Natalie Jackson Mendoza, certainly didn't hurt.

Will echo the love for the passageway scene; I'm not super claustrophobic but being in that situation would give me a fierce panic attack.
Really liked the monster designs and the fact we never learned their 'backstory' to any great degree; it seems unnecessary to me. I'll concede that the movie does lose it's way a bit when it turns into monsters jumping out from every corner and badass chicks destroying them with climbing gear, but it's nice to see an all-female cast not be stereotyped into the typical scared, running away and tripping every 5 feet scream-queens of most horror films and instead being just as rotten, mean, and deadly as any group of men have ever been.
Not to sound to sour about it, but people who are let down that monsters show up: I can't help but think it's wrong to fault the movie for misplaced expectations. I totally agree that the movie would have worked brilliantly without any sort of creatures and just been the characters dealing with the "stuck" situation, but none of the promotional material ever sold it as such. The "big" image from the film is a girl neck-deep in a pool of blood and the trailer clearly shows the camcorder monster arrival.. it was what it was. Though I know you didn't see any of that, Jake.

ETA: You know, I don't think that last paragraph really gets across any point I might think I have properly. Saying your expectations are off for not liking the monster stuff as much as the stuff leading up to it doesn't really make sense; you knew monsters were coming thanks to the trailers and such, it just didn't work as well for you as the rest. To which I say - fair enough. Good point. Valid opinion.
So disregard my sour grapes, please.