Viewers, and for that matter the BtVS crew, didn't know when Buffy jumped if the show was done.
Then Whedon found a new home and the show's darkest but most meaningful season begins with "Bargaining." "Bargaining 1 & 2" are not the show's best episodes. But they set up exquisitely the season's Big Bad by providing a reason for Buffy to wonder "Is this Hell?"
Season 6 is the show's most metaphysical. BtVS was always filled with symbols and metaphors, but with Buffy's asking of Dawn the nature of their existence, Whedon and Co. are taking viewers into the meaning of the story. In Season 4's finale, "Restless," Xander visits the "Heart of Darkness." "Restless" is well regarded for its prophetic elements and with "Bargaining" the journey prophesied begins.
Its a sad, brutal and pointedly banal ride. At season's end the world will be saved by the most prosaic object imaginable: A yellow crayon. But Buffy's question will remain: "Is this Hell?"