This is my favorite science fiction show. Really. It is that good. I didn't watch this show when it was airing in real time but it is on Netflix instant streaming. I powered through four seasons of 42min episodes and two miniseries/movies in a matter of weeks. It was an intense ride.
This show is very heavy on drama. There are a lot of sad, intense, painful moments, and yet I couldn't stop watching. The show builds momentum pretty quickly and never really slows down.
The series is about the survival of the human races, who's planets have been destroyed by a robotic race they had created long ago and actually thought dead until they suddenly attacked. The last humans are forced to flee into space with only one military vessel, a 50 year old ship with a small crew and only limited resources. As they fight for survival, the enemy is never far behind, and there is danger everywhere.