Overall thrilling film. The directing was creative, all-star performance from the cast, especially Sandra Bullock (as expected) and the pacing kept me on the edge of my seat.

Like many have pointed out, the film doesn't provide all the answers, but I'd much rather have that than excessive exposition. I see this method as "The Mystery Box" approach. It's much more enthralling to wonder what's inside an unknown box rather than rip it open and spoil the suspense.