To tell you the truth, this could have been better. But for what it is (if I even understood what "it" actually "is"), it's a powerful film, none-the-less.
I will not go into a synopsis of the film itself, but a review on my thoughts. I'm sick and tired of trying to find reviews, but are a complete synopsis of the film itself. (That is what IMDB, and Wiki is for).
The tone that was present throughout the film was one of paranoia. Which even by mid-film I started to question my own existence. By three quarters through the film I asked myself who the hell is the bearded psycho? And a little IMDB'ing was pleasantly surprised that it's Oscar Isaac! He looks totally unrecognizable with a beard!
Overall, I think the film is worth a watch. It's rated an 8 on IMDB currently, but I think it'll be an overall 6.something eventually. I watched it through the day, I don't think it's a night time film, as there are lots of long, drawn out bits, that could make someone fall asleep. Again, overall, definitely worth watching.