This film lay on the shelf for about a year, and was only released because one of the actors (Hemsworth) appeared in Thor, and writer/producer Joss Whedon directed The Avengers. Surprisingly, the almost forgotten movie became one of the critically most acclaimed horror movies in recent memory and a (moderate) commercial hit.
At first sight, everything is normal: five teenagers, two knock-outs, two studs and a nerd, prepare for a weekend in the woods. What's new, is that they're being followed. First we're made to believe that their actions will be filmed for a reality show, then it's suggested that they're smuggled into some sort of virtual reality (a virtual reality show?), and that's still not the end. It's only when Sigourney Weaver appears out of the blue, in the film's finale, that we learn what is going on. And still ...
Cabin in the Woods is not a bad horror flick. It manages to put you on the wrong track on several occasions, and performances are quite good for the genre. Of course the teenagers are played by actors in their mid-twenties (or even late twenties), but they were well-cast. For most part of the movie, the approach is tongue-in-cheek, with visual references to genre classics as various as The Evil Dead (especially part II), The Shining, Hellraiser and Ju-on (The Grudge). The horror is quite strong, but only near the end it becomes outrageously graphic, with rivers of blood and an incredible amount of gore. But even then the movie is not too scary. Some critics thought it worked best as an inside joke, which offered more laughs than scares.
Personally I think it's decent, but not great. The good atmosphere of the first half hour is not sustained, and like most of these postmodern, referential movies turning a genre inside-out, it seems more intelligent (and more original) than it really is. Another consequence of its postmodern nature, is that horror buffs might like it better than others. If you're one of those people who occasionally turn to horror, you might have mixed feelings (like me, 2x).