My thoughts (spoilers)
I just got finished watching this, and overall I like it, though I must say it rarely seemed like horror, which I'd chalk up to it being a high production, modern movie, and, of course, them going for the mystery elements.
I'm not sure if I like the idea of the transplanting more than the original, guessed idea of the black people being hypnotized, but I think it works better as a surprise, and does shed light on interesting interactions like the black "groundskeeper" hugging one of the older white guys that got out of the cars before the meeting.
I think the girlfriend made a great sociopath, so that was fun. I also mostly enjoyed the family and the tone of the movie, where it just wasn't quite clear what was up, and I can see how all of it would be completely unnerving yet also subtle enough where the guy had no idea what was going on.
Overall, I like it, and while it's one of the most modern non-horror horror movie I've seen, I think it works well, and I for one am happy about the quasi-happy ending. Bleak endings are fine, bit they can get depressing if every movie ends like that.