I don't think Ayers shaped Obama's political views or world view. Wright, however, I feel did and that's why McCain needs to let them let the dogs out on that one again. Partly because I don't think Wright can resist the temptation to get on TV to "clarify" and say something else damaging.
BUT Obama and Ayers are closer than the Obama camp and the New York Times article a few days ago let on.
The GOP Fact Sheet discusses it more, and yes it's the GOP website I know, but the fact sheet is just a collection of media quotes.