Saw this last night and was quite disappointed really.
Potential SPOILERS
I figured it out within the first 30 seconds so the film wasn't really all that tense or enthralling after that. Plus, when you are shown the twist towards the end of the movie, an action scene follows and then they do a flashback - what for? They must think we're really dumb if we need it explaining to us 5 minutes later.
That said Tim Olyphant was good (or should I say "outstanding" lol). I like Steve Zahn and think he has the potential to play a psychotic role, but he and Milla are wasted in this.