Very few. But then there are very very few Robert Bork's.
I do not mean this to be a shot at Bork, as I do respect the man on many levels. But he has a huge ego (I suppose if I was as brilliant as he was, I would as well). Thus he feels insulted that a person, he deems to be his intellectual inferior, is about to be approved for a job he was considered to be not suited for. That has to really irritate him, which is reflected in his comments.
On a side note, how many 'brilliant' people have you known, who had remarkable shortcomings in some areas? The mathematician with zero social skills or the college professor who dresses like he was dressed by Stevie Wonder on a bad day?
I do believe that an intelligent person, as Miers is, may just bring a level of knowledge and common sense to the position, that we will (hopefully) be thankful for in the future.
However, that does not diminish his perfectly legitimate criticism of Miers one jot, or make his strong reservations any less valid.
This nomination is a loser, and even the most ardent advocates of it realize that at some subconscious level.