I'm going to go ahead and say that "Cabin in the Woods" is an absolute MUST SEE!!!
This movie is so awesome. It works as horror. It works as comedy. It works as an intelligent satire. Holy crap, if you are even slightly a fan of the horror genre, I highly implore that you see this movie ASAP.
It drags on, slightly, at one part, so it's not at all perfect, but I'll give it an "A-", and that will likely put it in my top-10 of the entire year, when it's all said and done.