This is a great show! You will definitely get hooked upon watching the first episode (actually, it's a mini-series). I enjoy how the plot line is different with stakes at an all time high; the survival or extinction of the human race. Additionally, it's a great concept to intertwine this story with that of Earth making it more believable. You don't spend part of the episodes wondering, "Gee, that's quite a coincidence they also smoke cigarettes and know Greek Gods..." The visual effects are exceptional as well especially taking into consideration that it was a weekly television show.
My biggest issue with the show is that during the beginning titles, dramatic points of the episode are revealed in quick snippets. Some may enjoy that, but for me, I find it ruins part of the surprise and pleasure of anticipating the characters' next course of action.