Excellent film. Not really a Horror, more a Teen-Thriller.
Joss Whedon perfectly balances Thrills with Comedy and a Cheeky wink! Great!
To me it was Joss Whedon at his best. The humour and cheekiness, the many monsters, gunky stuff, the evil below,etc etc. All the stuff he did so well in Buffy and Angel. I think showing us the men in suits at the beginning, made it so much more interesting and made me feel it wasn't going to be your run of the meal, group of people killed off one by one while staying in a shack type thing! Which was what I originally thought it would be.
I loved it, I agree, excellent film.