All I could say was wow when I left the theater after watching The Hills Have Eyes. It had a few small flaws like all horror movies, but overall was done VERY well. It had several opportunities to go corny or just plain stupid, but it didn' take any of the opportunites.
I won't spoil it but lets just say it has a period of about 10 minutes that just knocks your socks off. At first your like "That's terrible!", then something else comes along immediately and you go "Oh my God!", and then something else, and something else, and your like "Can this family be violated in every possible way any more than it already has been?", and it does.
I haven't seen a huge amount of horror movies because I don't like corny stuff, but this is the best one I have seen just off the shock factor and originality alone.
It won't keep you up at night, but you won't forget it for a little while.