I'm not a big fan of hard-core bluegrass, since it seems particularly prone to the "fast and flashy is everything" syndrome in music. One of my favorite guitarists is Norman Blake, though. It seems that on his albums in recent years, he has been slowing down and doing wonderful, soulful versions of oldtime songs (listen to "Chattanooga Sugar Baby", for instance). I don't think it's because he CAN'T still play fast - I think that it shows he's matured as a musician and appreciates that he doesn't need to.

Or as an old quote whose attribution has disappeared into my memory morass would have it:

"I shore wish I could play all them notes - and then not do it..."