I assume the movie will be good. The new official trailer is amazing. Check it out: http://www.filmabend.info/horror-im-kinosaa-paranormal-activity-trailer/
This is an excellent little movie, very quietly creepy.
Personally, I think the less explanation about this movie you get before watching it the better. I lent it to a friend of mine with no other instructions other than to "watch it in the dark." She was not happy with me.
I highly recommend it.