LOL This is most definitely erotica that appeals to those who like threesomes. Well written and hot (and, no, that's not my cuppa but I can appreciate it nonetheless).
Lovely hot piece that begs for more if only to see Riley get his (or not, as the case may be).
It was hot and I really liked the use of the characters and how they related to each other. Different friendships and marriages, all described well. It made me curious about them. I can't feel sympathy for any of our main characters though. Non of them as any moral high ground.
Truthfully, that's sort of how I wrote it. I wasn't expecting there to be any sympathy because there really can't be. What they're doing isn't right, regardless of motivation. As loveably as Spike, Buffy and Cordelia are, as you say, they don't have any moral high ground for this one.
Now I could see the banner, looking good.