Personally I loved this movie - it was one of the best new horror movies I saw this year. I understand that people would say that it is not original (I agree with them) but I do not think this is always a criticicm. After all most movies are not original (particularly in the horror genre). It's all about the presentation - in this case the script was constantly surprising and kept me offbalance. The director staged the scare scenes extremely well and took the time to build a foreboding atmosphere. That sequence referenced by the other posters was scary and unexpected.
There's always free cheese in a mousetrap.