This is one of those movies that, after watching it, you will keep thinking about and coming back to even months after viewing. The acting is spectacular for starring two children (I usually hate movies with whiny kid acting). Bill Paxton is awesome, his directorial debut is even better than what I expected of an actor whose most memorable line is "Game over, man! Game over!" (from the movie "Aliens").
The best part about the movie is the dichotomy between those scenes where the actors play a family, and when they are doing their "work." It really makes the movie believable and memorable.
Keep it up, Bill. I'll be waiting for more movies I"m sure to love!