Here's Dana Goodyear (she used to be the Poetry Ed at the New Yorker, but I think now she's a staff writer?) quoting Sarah Silverman:
I don't know much about comedians --they kind of frighten me in their willingness to endure humiliation. The whole thing seems pretty awkward to me. Silverman, though, seems pretty damn funny in a caustic way.
more: TMFTML of Sarah Silverman/NYer article. Unlike me, he's gonna actually talk about the substantive issue in the article: can racist jokes be funny?