I don't think it is techinically supposed to be called a 'horror movie'...I wouldn't call it that at least. It is much more like a psychological thriller, and those can be insanely intense. I thought it was awesome, some of it was predictable (like the trap door, noticed it when the guy got clubbed in the head and his blood was in a straight line) but it was awesome. As soon as they got to the end of that hallway and they were groping the wall I got it and was just like OMG! lol. It was awesome, though the girl won't be a good jigsaw, doesn't have the awesome voice, but i'm not sure if he is dead or not...Anyone notice the used saringe near the trap door at the end? I've been trying to figure that out lol.
Another movie somewhat similar is mothman prophecies, not as good but still creepy.