Having been a fan of "hard" science fiction literature for a lifetime, I have learned to leave my critical assesment skills at the door when it comes to movies. I expect only fantasy or space opera and so am seldom disappointed with a screen translation of even a favorite book. "Signs" falls into that category of breaking the rules of hard science fiction, yet it seems to work as entertainment in the general category of science fiction. Since we come to this forum as home theatre enthusiasts using Outlaw gear, let me be the first to praise the subtle but well engineered sound track. The attack on the farmhouse used precision surround sound in a masterful way to produce an atmosphere rarely seen in previous offerings.
From previous comments in this thread, I get the feeling that there are a few "hard science fiction" enthusiasts out there and would be interested in comments on other movies that satisfy.