SMG
Yeah, they do mention her... and usually it is about her professionalism and workaholic-ness. Other than that, it's about aspects of shooting the scenes. (For example, there's mention that in Hush, she screamed her heart out but they couldn't use her scream for some reason and had to dub someone else's voice over it.) The best comment I heard about her was Joss saying that they just knew she was Buffy, she fit perfectly into the role when he was casting.
I think there was bonding between SMG and DB at least - I remember reading about their "breath-offs" just before kissing scenes - they would eat funky foods to make their breath worse than the other person's. (Hmmm... does that count as method acting? The pain,the pain... Maybe that's why I was never too sold on the B/A romance.)
Also, everyone tends to blame SMG for the end of BtVS. I seem to recall an interview with Joss where he said that when Sarah approached him about not renewing her contract, they made the decision together to end the show. In other words, Joss was as ready to stop as she was. As much as I miss it, I have to say that they did the right thing - they went out on top.