Great premise, but botched execution *SPOILERS*.

Rating: 6/10 (25 May 2015)

The premise of the film is absolutely amazing, but sadly, the execution of this was severely botched. We see the purge from the perspective of one family inside one household. That's it. The whole film. There is almost no action and almost no killing.
So the film is enthralling and you actually wonder, are these people going to make it out alive? Everything falls apart when the family's stupid son lets a total stranger in the house by lowering the shields. Does this strange-looking child have a single brain cell?!? This makes the house a prime target for a man and several masked killers. After some filler, the masked men get in and a huge action sequence starts. When the sun is setting, you feel the tension rising and you can almost feel their cabin fever. This gives the film lots of credit from me.
But then the second half of the film is just... infuriating. I lost count of the number of times a character was almost killed and then was saved at the last second by divine intervention. In real life, they'd all be dead within an hour. Simple. Yes one can argue it's many people in a small house, but still, the chances of THAT many divine interventions is less than those of being struck by lightning twice in one day.
This was infuriating to watch, and became more so after every time this happened. Which was pretty much constant during the second half. And of course, surprise surprise, it's the father that gets killed. Because it's always the father. We all saw this coming. Could this have been any more predictable? It was a real shame. I really thought they would throw a curve-ball and have the kid that started all the problems die. Or how about have them ALL die? That would have been certainly a subversion of expectations. But nope, we just get the head of house dying. And the girlfriend who didn't even need to exist in the film.
So I have highly mixed views on this film. 6/10 for the absolutely amazing premise and the 60% of the film that had me along for the ride, but minus the 40% that was one big cop-out.