We can all see the obvious similarities between this and Paranormal Activity - so let's get that out of the way. They both have their charms and I actually enjoyed both - this one is based on the same type of horror as it's counterpart but deals with it in a slightly different way. If you enjoyed Paranormal Activity (or haven't seen it) then I think you'll like this one.
Having already seen Paranormal Activity - I got the same feeling watching this one. I'm not sure what it is but the "documentary-type" filming really pulls me in, especially in these home environments. It does however attempts bigger scares throughout the movie than P.A..
It's not a movie I will watch again but it was a fun ride.