Yeah it was a great season finale and should have been a series finale - it was the perfect ending to the five season story arc that Eric Kripke had.
But as always, money talks and it has been renewed for a sixth season, although Kripke has given the showrunner status to Sera Gamble for what I gather will be a return of the 'monster of the week' storylines. Which isn't a bad thing because I loved season one and Gamble has written some of the best episodes of the show. I just hope that it doesn't degrade the show a bit because overall, it has been consistantly great.
As for the finale, I was expecting something a bit more explosive and action packed but the slower pace worked brilliantly and those montages of Sam and Dean's lives, and the impala were superbly done, really emotional. I'm glad Castiel and Bobby didn't really die but it'd probably be better if they weren't so easily brought back to life, just seems like a cop out, of sorts.
Do you reckon Chuck was God btw? And what was Sam doing at the end? Great episode, great series.