It started out with turbo speed and I really enjoyed season one - lots of action, an intriguing and intelligent storyline with several interesting characters and a lot is going on from ep. 1, but season two was... well... not so good.
It got too complicated, and it got harder to follow all the different stories in the main story. I do not mind complicated at all, but when it starts to fell messy and made in hast and putting too many new characters in the plot, you loose the character development of the original characters, and that's a shame, because there's a lot more to be discovered and exploited from the originals - it's like we only got half their stories.
But let's see what season three will bring - I personally hope they'll go back to first season's great script writing.
I was sceptical in the beginning, but I think it picked up speed in Season two, and it has turned into at least a semi-decent show, right up to where all the teenage love story crap began - what a shame! :-/