Hmm, I thought Lioness might have popped in here by now.
I'm going to put this whole post in a spoiler, because I'm really rusty on Buffy, and I don't want to spoil anybody by accident.
Spoiler (Highlight to read):
I love Buffy... up until a point. By the end, the term 'jump the shark' doesn't even BEGIN to cover it. They had made at least five laps of *that* pool. Honestly, Buffy dies like Cher goes on 'farewell' (she's doing Las Vegas now! XDDD) tours, Dawn is the most annoying character ever conceived, and Willow the Teenage Witch was horribly judged IMHO. Maybe if they had hooked her up with Harvey Kinkle I'd have understood - but Tara?
In the final two series I thought the quality of writing took a real nose dive, and what had been relatively well-rounded characters became functional archetypes. Buffy was great in the first five series because it was character driven, although by series six the characters had become subservient to the plot.
Spike really should have left earlier as well. I've never really been to fond of that character, although when I think back to when he was with Drusilla, there was actually a really interesting dynamic to that relationship. They had a strange relationship in that although they were sleeping with one another, they were in many ways mother and son. And then when Angel arrives (who could easily be considered a father to Drusilla; at the least a dominant male) there's a classic Oedipal conflict between the three of them.