This movie was released on DVD, in January, and I just now - finally - saw it. . .
I must say that this film was totally worth the wait, and even though it was released [in the UK] in 2008, it definitely has the potential to make it on my 'best horror list' of 2009!
First of all, I was totally enamored with Kelly Reilly [an actress that I am unfamiliar with] She was great in this movie - she made her character totally believable, and made the film well worthwhile. Not only was she great, the film was fantastically written - this is definitely an intense film! [I kept saying to myself - "Just let it go!" or "Hurry!" or 'Get out of there!", etc - always a good sign] ;-)
If you haven't seen this one yet, it is definitely recommended - just keep in mind that it is a brutal film, that involves teenagers as the antagonists.