Palin definitely avoided any major gaffes, and she certainly defied expectations that she'd fall flat on her face. But her performance was nevertheless somewhat flat. Stylistically, she was fine. But her style wasn't strong enough to cover up her total lack of substance. And her statement up front that she wasn't going to answer questions in a way that pleased the moderator or her opponent just highlighted her dependence on talking points. She would have been better off not responding to questions, rather than not responding and acknowledging that she wasn't responding. I suppose that might have played well with Rush Limbaugh--and anyone else who wants to stick it to the MSM--but I'd imagine voters weren't all that impressed.
Biden, meanwhile, gave a strong performance. You got the sense he almost had to restrain himself from going after Palin for her lack of substance and her misrepresentations of Obama's record--and sometimes he failed to restrain himself--but he certainly didn't cross any Lazio Line and come off as a bully. And, substantively, he was clearly the superior candidate. Throw in his emotional moment in talking about his sons, and I'd actually say that of the four debate performances so far--Obama's, McCain's, Palin's, and Biden's--Biden's was the best. Too bad, for the Democrats, that this was his only one.