As a season finale, it was pitch-perfect. Although, at some points, it felt kind of like a series finale (mostly Chuck's story of the Impala and his narration at the end). If they hadn't gotten the sixth season, I don't think the finale would've been much different, except of course the end: either Sam would've been stuck with Adam/Michael and Lucifer (BAD ENDING), or else Sam would've somehow managed to separate himself from Lucifer (maybe with Michael's help?) and then the boys are happily ever after the end.

But I am so glad that there's a sixth season! Can't wait!