Buffy utterly surrenders the moral high ground as soon as she decides that she should murder Faith to save her "lover". The fact that she fails to actually kill Faith does not mitigate what she does. This is no Ted situation when she was acting in self defence, this is murder. That said, the fight between Buffy and Faith ending with Faith toppling from the balcony is a brilliant BtVS moment.
Other thoughts: did Joss and co always mean for Wesley to be right all the time? He may be a pompous ass but he's a righteous pompous ass. I loved the exchange which cumulates in Willow asking if one of the tigers is coming. I'm not sure if I like that they made Faith murder the professor in such a cold blooded way. It makes her almost irredeemable despite that she is, erm, eventually redeemed. I love the return of Anya played wonderfully by Emma Caulfield but I do wonder at her characterisation: 900 years of helping women with their vengeance would surely give her an exceptional insight into human behaviour and not, in fact, the opposite.