I didn't really enjoy watching it, but it had some great ideas. I just didn't like the characters at all. So, when I don't care about anyone, and there is no difference between being dead and being alive, there are no stakes to add tension of any kind to the film.
I kept wanting to like it so bad. It seems like something I should like, but it just never seemed to work on a basic level. I do always appreciate people trying new ideas when making movies, even if it is in a genre that has been way over done.