Go see it, and it'll be very, very likely that you'll love this film.
That said, if you've lucky enough to have seen it already, want a reminder why it was so much damn fun the first time, and live in the US (stupid region coding, this particular Canadian can't even watch this!) or know a lot about proxies and spoofing your IP address to watch protected content (I AM NOT ADVOCATING THIS!), why not check out this link from those kids at MTV that used to play things called "music videos".
Cabin in the Woods opens wide on Friday, the 13th (!) of April.