dw_moffett, the star of Traffic and Thirteen, has just recently filmed a guest appearance on Brothers and Sisters. He talks a little about the character he played and what it was like filming with Calista Flockhart and Rob Lowe. You can check out his LJ if you're interested. He loves to answer questions, so feel free to ask him some if you like.
I don't know if talking about his character constitutes spoilers, but be aware that he does talk a little about it.
Anyway, just thought I'd post about it. I'm x-posting to a couple of places, so apologies if your flist gets cluttered.