I just saw the pilot episode last night. I thought it was pretty damned enjoyale. I'll continue watching this show, until the end (or at least until it's cancelled).
About the whole "What about the comet?" debate. First, as was mentioned a few times, it's a seperate time stream. There's no garantee that the comet is even gonna hit the Earth. Even if it does, it's not gonna happen for another 20 million years. Asking how the characters on the show are going to survive the comet's collision is like asking me how I'm going to survive when our sun going supernova in 20 million years and burns the Earth to a crisp (answer: I'm not because I'll already be dead and fossilized by then). It's a stupid question. And finally, suppose the descendants of the collonists have to survive the comet's collision with the Earth 20 million years later. Unlike the dinosaurs, they'll have the ability to build fires and shelters. They can stock up on food preserves before the comet comes. Given enough time to prepare, a person (or a community of people) can live a long time without fresh vegetables, and can eventually survive without fresh meat. So long as they have preserves and suppliments to last until the ice age ends.