It is rare that any TV series can keep things consistently fresh and interesting through seven years. Supernatural has done that - and I think this has been their best season yet.
It wasn't just that this season had the most interesting and entertaining episodes. They had a good mix of episodes (both stand-alones and "mythology" episodes) and a great villain: the leviathans. Nearly impossible to detect and nearly impossible to beat. Nearly impossible to beat. Every creature can be killed, and while Sam and Dean worked on figuring it out, they found a way to slow the leviathans down considerably: borax and a beheading.
Plus, I loved the way the leviathans' jaws unhinged.
Then there were some awesome "stand-alone" episodes: the mini Buffy and Angel reunion between Charisma Carpenter and James Marsters; the trip to the most "psychic" town in America; the ridiculous "Plucky Pennywhistle" episode which mixed two significant fears of mine: clowns and children; Felicia Day as an adorable lesbian hacker; and "Season Seven, Time for a Wedding!" which stands as my favorite title ever. Supernatural has never been funnier than this season.
I wasn't crazy about Castiel's absence for the majority of the season. Evil Cas was fun but I feel like he wasn't maximized. He unleashed the leviathans and then faded into the background until the end of the season. While I liked his return, it felt like a wasted opportunity. On the other hand, I thought Bobby's death, return, and final death was beautifully handled. I love Bobby and hate to see him go, but if he is going to leave, this was a perfect way to do it.
It looks like season eight might bring it back to a dark place. When we left the Winchesters, they had been separated. Sam was still in the real world, but Dean and Castiel are stuck in purgatory. Is purgatory worse than being locked in Satan's hell box? I don't like it when the Winchesters have separate storylines. It is depressing and maudlin and it robs the show of its humor.
I am also bummed that showrunner Sera Gamble will not return for season eight (she will have a "consulting producer" credit, but that is practically meaningless. That is the title they gave Community creator Dan Harmon after NBC shitcanned him). Sera has been with the show since season one, has written some great episodes, and really feels like an integral part of the show. Change happens; I get that. Taking her place will be Jeremy Carver, who left Supernatural to develop the BBC show Being Human for American television (with debatable results). I enjoyed his work on Supernatural more than Being Human, so hopefully he won't have picked up too many bad habits.