I can understand why people got nauseous watching this movie, but if they paid any attention at all to the trailers, then they would know that it was made on a hand held camera and could make an informed decision.
I personally thought the movie was effective in the way they were able to build anticipation and use simple sounds to create terrifying effects. I went home after seeing the movie and was spooked by the most harmless of sounds that normally I wouldn't have noticed.
This movie is not a gory horror movie. It is a suspenseful thriller and was brilliant in it's simplicity. I highly suggest everybody check it out!