I think it's a really original movie. Not story or narrative wise but rather the way the story unfolds. It almost unfolds backwards and has you use your mind to piece it together rather than the film straight-forwardly showing you a beginning, middle and end. Its really smart storytelling. Some people think this movie is slow but I think it builds atmosphere for the scares really well.
The scene with KaDee Strickland being followed by the spirit is my favorite scene. Overall a great horror movie and worth seeing.