Palin was playing the standard game of Liberal Gotcha! Trouble was, she was short on accuracy, and Biden was much, much better at it and far more credible.
McCain supporters were simply looking for her not to fuck up too bad, and she delivered on that. As for substance, accuracy, or the wisdom of any of McCain's proposed programs, well, that fell predictably short of the mark.
Biden did a great job of looking genuine against Palin's coached, talking point ridden, beauty contestent performance.
I predict that Biden won over a significant portion of undecided voters with his straight talk, emotionally open demeanor, and better understanding of what actually plagues the middle class these days. Palin's performance won't erode McCain's support, as a more stumbling performance might have, but I doubt it will garnish much additional support, either. I know the popular wisdom is that large percentage of voters don't care about the issues (don't understand them seems more accurate), but Biden clearly bested Palin on both substance and genuineness.