So how scary is it?
I'll tell you this. I saw it in a packed house. During a particularly tense scene, the ushers, as a joke, decided to bang on the doors. The audience levitated and took a good minute or so to laugh, catch its breath and settle back into the movie.
We were caught by surprise because we were involved. I won't say that I forgot I was watching a movie but the movie had my full attention.