I saw that too. But put Obama in a comforable evnironment like Oprah and Late Night, he does fine. But as soon as tough questions are put to him (that are not scripted), he falls short of the mark.
(And BTW, after this election is done, I hope Palin tells Oprah to take a hike! Oprah doesn't want to be biased, hell, she's already chosen a side. But then again, it's her show.)