(no spoilers, honestly)
Battlestar Galactica is brilliant. I'm not sure how it ever made it to four seasons, being largely impenetrable for any one who hadn't seen it from the start. It was brave enough to be a sweeping space epic when all TV networks were interested in was hospital dramas. And it moved along at a rapid pace, only very occasionally resorting to episodic fluff. The writers had their hands on a genuinely compelling plot and they weren't afraid to completely and unexpectedly turn it on its head. It's one of those rare shows that isn't afraid of killing its characters, there was a real sense of risk that's usually missing in television. I admire a show that is so full of ideas that it can barely contain itself, always moving onto something new like it knows there isn't much time, never letting itself be cosy or predictable.
Science-fiction is a genre that can be incredibly dull, resorting to an episodic structure to attract new viewers (what Joss Whedon would call 'reset television'). Done properly it can have a deep and dangerous arc that can captivate its fans. It can be pretentious but completely engaging. It can be, in the truest sense of the word, epic. This is science-fiction done properly. It's over now. Which is a shame.