Lotsa great stuff here! One thing that Jon Freeman mentioned was musical playing instead of technical playing, which sorta aluded to was why play fast anyway? If you listen to Norman Blake over the years (and I think I've got everything he ever did) you'll notice that he can pick about as fast as anyone, but quite some time ago he gave up speed in favor of feeling. And I for one think he sounds better for doing so. And I also agree that Doc Watson uses his left hand as effeciently as anyone I've ever seen.
BTW, has anyone ever slowed the really fast numbers of Beppe Gambetta or Carlo Aonzo? I'd be willing to bet that Carlo doesn't miss a single note - that's speed and musical talent!