The 50/50 split of 5 star and 1 star reviews makes a ton of sense. This movie hits a very specific nerve: one that not everyone is sensitive to. If you are, this movie is absolutely gut wrenching. If not, I'm sure it just seems depressing and dull. Personally, I came out of the movie absolutely weeping.
This movie is similar to Donnie Darko in that the horror is there, but it's very subdued - there are creepy visuals and horrifying premises, but there aren't many (or arguably any) blatant scares. This is the kinda movie that fills you with dread, not panic.
There are a few scenes that last longer than they necessarily need to, but all the stuff that you'd be cutting in order to make the scene more efficient is so gorgeous that I tended not to mind being shown jt. There's a fine line between boring and atmospheric, and in my opinion, the movie manages to stay in the atmospheric side far more often than not.
If you want a fun horror movie, this is not it. But if you want something that makes you feel, you've found it.