When it comes to preparation, sometimes there really can be too much of a good thing.
On the one hand, Sarah Palin sounds prepared and competent right now. On the other hand, she really seems to be simply repeating talking points. And every candidate does this, but some -- like Joe Biden right now -- can make it seem spontaneous and unrehearsed. She sounds overrehearsed, even robotic. It's OK to sound that way as she gets warmed up, but she needs to loosen up as the debate goes on, or people will be less likely to revise any unfavorable opinions of her.
By the way, is anyone else watching CNN and absolutely fixated on its graph showing the real-time reaction of a group of uncommitted voters in Ohio? What I find really interesting is how high the numbers go whenever either candidate talks about energy independence. (Though, interestingly, it looked like women hated Palin's resurrection of the "Drill, baby, drill" line, while men liked it.)