Great series. The biggest drawback is that you cannot remember the details in between the seasons so previous seasons have to be rewatched. I rewatched season 1 just before seeing S2, and now will rewatch both seasons when S3 releases. It's rewarding in it's own way, but I would not recommend anyone to start it now, better to wait until S3 is released and then watch in one go, as it is the final season anyway.
I find it tough to rate TV shows, but both seasons would get 4.25 from me.