Why Do People Either Love or Hate This Movie?

I saw this movie with a group of friends recently and half of us loved it and the other half hated it. We were torn through the middle. I loved the "you don't know how it's going to end and twists and turns from all directions" while my buddy said it dragged on. I don't get it. And as far as the bruise on the face, it's only on the opposite side when she's looking in the mirror after the first "incident."

But it's still strange that it's one of those movies where people feel so strongly one way or another. There's no middle ground.