I'm not caught up on this, so haven't read much of this thread, but wanted to jump in and say that Season 2 was seriously good!
I nearly didn't watch any of this, as the first episode (S1) was so, so bad, but stuck with it as I liked the premise so much. S1 was, on the whole, decent but not great. S2 was, other than the odd heavy-handed character arc (Finn, Clarke's various switches) and some very dodgy science (just don't think too hard!) a major step up.
Just starting on S3, couple of episodes in. The setup isn't grabbing me as much as S2, but will be a nice change up.