I think the biggest mistake was the whole season 6 arc; Tara dying and Willow getting her death's revenge was completely out of Willow's character; she wouldn't have done that if that season arc were to be written by writers who knew Willow's character. Also, there is something bugging me about the arc of Spike/Buffy relation in the connection of Season 6 and Season 7; in the end of the Season 6, Spike attemped raping Buffy (yeah yeah he stopped himself in time, how blessing isn't it, I mean since he didn't rape her when it was his aim at that moment, he should be a hero; he is a gentleman after all) and in Season 7, Buffy didn't even mention it and put it behind. Why was it? Because he was mad? Or because she was mad? What happened between Spike's attempted rape and Buffy not talking about it? It was a weak character portrayal. Of course, Season 7 is full of them; potentails weren't even portrayed as characters, and it was a fiasco. They were not recurring, they were there all the season so why not deeply examine them? And if they are not worth being examined deeply, why put them there in the show, in the LAST season? It was the last season and we were kept busy by a crowd (potentials) and couldn't consentrate on the core group, it wasn't how it happened in ATS, and I am happy for that. But the "fight keeps going" or "fight never stops" mottos were deserved by the Buffy the Vampire Slayer.