Biden could easily be President. He seemed presidential in his carriage and presentation (as does John McCain), and he clearly has extensive experience and a broad knowledge of all the topics discussed.
I don't see how, when Palin's competence is in question, her refusal to answer the moderator's questions can be seen in a positive light. She said at one point (I paraphrase) "I may not answer the questions the moderator asks or in the way she'd like, but I'm just going to talk straight to the American people." Why not make a "straight to the people" answer of the question presented? I for one have had too damn much of politicians telling me what they think I would rather hear over the information requested of them. The issue of whether she is even ABLE to answer the question she was given thus remains front and center. Biden also dodged his questions (though to a lesser degree), but his grasp of the issues is not questioned by anyone, even if people disagree with the conclusions he has reached. The answers Palin provided were rehearsed and junior-high-school basic (struggling with names a bit and saying "nukyuler"), and it's my strong impression that if one asked for details the house of cards would fall.
Her highly questionable suitability reflects badly on the judgment of John McCain. We can, and should, demand better.