A nice idea and very well executed. Unfortunately it doesn't have a lot of redeeming elements, especially in the conclusion, for horror fiends like myself. It lives you thinking, but only for a little while.
It wasn't a flawless film by any means, but it was the best in the franchise since Aliens. It opened up the series into so much more potential. Can't wait to see what's next. The fact that we got something THIS new THIS late in the game is mind-boggling.