I'm someone who actually really enjoyed season 6, i think a couple of episodes in that season will be looked at as the best in supernatural's history when the show ends. The season premiere of season 7 should also join that exclusive bracket.
An episode that felt like it had 4 episodes worth of material in it. Castiel turns evil, then turns good (sort of) and then ends up evil again (although not at his own free will this time).
Dean has been pushed to the limit, as can be seen by the way he treats death and also Cas (he did deserve it though) in this episode.
Sam turned into somewhat of a love/hate character in season 6, although i loved his soul less character. He continues to redeem himself here, although the writers seem to be pushing him a bit to the point where he is too good right now.
Great start to season 7, and i'm looking forward to what should be an entertaining and unpredictable season arc.