I had been waiting for @travisg to review this and give it an A so for the first time I could agree with him!
All joking aside, saw this opening weekend and yes, it is a very strange movie, right down to the format in which it was filmed. The overriding sense one gets is of claustrophobia and a mounting dread. Less of a horror movie (as some have labeled it) than an exercise in dark psychodrama. Willem Dafoe delivered an Oscar-worthy performance, and I have a newfound respect for Robert Pattinson. I walked out of the theater not really sure what to think, but after taking the time to process found myself admiring the film more and more.
Definitely refreshing to see a movie that steps outside the proven formula and takes a chance on challenging the audience. Highly recommended.