First off, you have to understand the dynamics of a found footage film to watch this movie, otherwise you'll hate it. For me, I like them in general (I LOVE Quarantine, an awesome concept with a great cast, and am meh about Blair Witch - all those jumpy camera shots make me nauseous).
This one felt very real to me, like it really was recovered video from someone's camcorder. It begins with one of the character's 'short films', which almost lost me entirely, but once that was over and I understood that the following footage was that character's, the "filmmaker"'s, perspective, I was along for the ride. The characters are fun, and often pretty funny - overall, the actors seemed really committed to making this zero budget movie come to life. The one dude in particular was really convincing and scared the hell out of me at the end.
The "twist" was all right - in fact, you could see it coming clearly, but there were some red herrings which threw you off. The final reveal was creepy, and I legit was freaked out by the one actress ( I won't spoil who...) - overall, I really liked the cast.
The camera work was actually pretty decent, and almost seemed like they were going for a "cinema verité" feel. The action did lag a bit in the middle, but definitely picked up in the third act, and had a cool climax.
Again, if you don't like this style of film, avoid this flick - but if you want to see a bunch of kids killing each other in the woods, this may be for you. I liked it.