A little non spoiler info about the movie first. It is filmed like blair witch, though it doesn't have near the jostling of the camera that Blair witch had, so no dizzy moments for those that are sensitive to it. It is filmed like a documentary. So don't go into this movie with notions that it competes on the same level as other typical scarey movies.
The movie does a great job making you believe that the people shown are just normal people. There are a few points that you will have to suspend a little disbelief as far as comparing the main characters to yourself and how you would react, but definitely no where near that of a typical horror flick that has chase victims running upstairs instead of through the nearest door or window.
A BIG HEADS UP: This movie uses a lot of silence, as many of you audiophiles know, the use of silence in movie recordings can be very important. I would avoid whatching this one in a movie theater that is packed, especially with a bunch of highschool teens that can't keep from squeeling long after anything scarey has happened. It is a movie that is easily ruined by people that are talking, shuffling candy wrappers, or with people trodding up and down the theater stairs.
The documentary style story, and filming technniques are done well in a believeable manner. The movie sounded great to me, though this is subjective since I only saw it in one theater (AMC) I believe it could honestly sound amazing on a home theater that makes use of a solid subwoofer.
My recommendations since I rate the film at 4 stars out of 5, and given the sensitive use of silence and subtle sounds, I would recommend that you stay away from packed movie theaters, and enjoy this one once it come out on DVD/BR instead of running out to the movie theater.