To me an exchange like that works in Hillary's favor. Most people are already inclined to see Hillary as a complex and flawed figure. But--not to sound like a red-faced Bill Clinton here--I do think a lot of Obama supporters haven't had much exposure to some of the tougher critiques against him. (Incidentally, Obama's answer about his ties to Rezko, which focused on a small amount of legal work he did, also conveniently ignored a more significant connection between the men, which was the land deal that Obama himself has called "boneheaded.")
That said, I do think Hillary has taken some unfair shots at him tonight, about which more later.