I went to see this last night. I thought it was fairly average. Not bad. On the plus side I thought in certain scenes Jennifer looked really creepy. There was some nice gore and a couple of good chuckles ("Am I too big?"). And I'm in the pro-Amanda Seyfried camp, I thought she ws really good in this. And of course Megan Fox looked hot, though I think Amanda Seyfried is nicer looking. And the girl on girl bit was quite horny
On the negative side, I never really bought into the relationship between Needy and Jennifer. It needed fleshing out. I can understand the comparison with Ginger Snaps (I was thinking of it myself) but the relationship between the two sisters in that was a lot more convincing and it really made the situation that much more heart wrenching. In this I never really got the impression that Needy really cared about losing her friendship. I put that more down to the writing and direction than the lovely Amanda's performance.
Also I was a bit confused to the exact nature of what was happening to Jennifer. It didn't help that we don't find out what happened to her in the van until way into the film. I mean, was she possessed or did she just become evil? Why did she need to seduce the guys so much? She said she needed them scared, did she need them aroused as well? If so I don't remember it being mentioned. What I'm trying to say is, when she had the boys alone, why did she continue with the seduction? Why not attack them straight away.
And the ending was mightily disappointing. It was making out like it was leading up to a Carrie style high school dance massacre, but it never materialized. The ending (both the scene by the pool and in Jennifer's bedroom) were just a bit drab and lacking in excitement.
And I also thought the scenes in the mental home were crap and, actually, unnecessary.
Despite the cons outweighing the pros here, I still thought it was ok. Sorry, I've gone on a bit.
Bring her to me, you bum. I'll take care of business.