I went to Oxford, where they give you actual 3/2/1-on-1 tutorials several times a week. You get to sit in a comfy room with an actual world renowned professor in the appropriate field.

Great as it sounds, I think the main benefit is accountability rather than better teaching. You don't want to be the guy who wastes an hour with the fellow of the academy of sciences.

As for teaching, such people tend to have more of a bird's eye view of things than is good for teaching. They don't know a whole lot about the details of the subject anymore, their job is to find funding. The best teachers tended to be recent PhDs.