Just finished it. I really liked it.
I liked the concept, I thought most of the acting was really good, especially from Bullock and Malkovich, and I liked the way it was structured. There were some moments of plot convenience, but nothing too damaging.
I appreciate it as one of the more rare films these days that act as allegory. I spent quite some time talking with a friend afterwards about the deeper meaning and symbolism; what the entities represent, what the blindfolds represent, the birds, other elements of the story... And that's a rare thing. Most movies these days are cheap, fast food for the senses and instantly digestible. It's quite uncommon to see something that warrants serious analysis of theme and depth afterwards.
Anyway, I dug it. I'd give it an 8.7.