Yes we have seen Seth. We are in the middle of the 3rd season. Seth is really cool. His lines are very carefully crafted to keep him both cool and intellectual. We like the line in the 6th season where Xandor says "I almost saw you make an expression" and Seth said "I felt one coming on, I won't lie".
Cordy's character can be summed up in one line she said to Giles, after he accused her of being tactless. "Tact is just not saying true stuff. I'll pass." :)
Is it possible that Anya said that. She took the lack of tact thing to a whole new level. I bet it was Anya.
We just saw the ep last night where Willow accidently brings vampire Willow into this reality. We had to pause the TV for laughter there were so many funny lines. At the very end they sent evil Willow back and 2 seconds later she backs into a stake. She looks down and mouths the word "Ffff" and disappears. It was great. Ofcourse you can't help but kind of like evil Willow. Nice willow said "I think she's kinda gay". Angel started to explain something about how your vampire self is not different just less inhibited and then he just said nevermind. An early hint at her lezbo-ness. I'm sure it was planned from the beginning.