The first few seasons of season 1 I think are pretty poor, but other than that I really enjoyed the first two seasons. It's definitely a CW show, because they ride the 'forced drama because no one can ever get along with anyone else for more than two seconds' train pretty hard, but there's some really great stuff there. The ending to season 2 (which I won't spoil) in particular I think is genuinely one of the best things I've seen on TV. I sort of lost interest sometime in the third season though, when it seemed like they tried to drive that train through the station one too many times and all the characters starting making stupid decisions and regressing in their development.
Might just be me, though. I know lots of people still watch and enjoy the show, and who knows, maybe seasons 4 and 5 are better.