I found these blog posts by David Friedman and Bryan Caplan interesting in that they have differing takes on Barack Obama, even though both seem to like him.
Friedman's take is that Obama's positions are closest to libertarian of the three candidates, so Friedman therefore prefers him (although he says in a comment that he will still vote Libertarian). Caplan also seems to like Obama, but says that his likeability is more likely to help him get his way, resulting in bigger government. He'd prefer to have someone like Clinton or McCain in office, on the grounds that it would be more difficult for them to get anything done. Both strike me as reasonable positions, although I think I lean somewhat closer to Friedman's view.