Saw an advanced screening of this movie wednesday night. Really good film! All the characters are likeable, there are some good scares, intense atmosphere, good story, good pace, and a fun movie going experience. I'd say this is better than a Paranormal Activity because it is faster-paced and the suspense builds a lot better. I'd call it a modern classic and say it's James Wan's best film along with Saw.
See it in the theater for sure if you can. Memorable moments throughout and I will probably see it again opening night.