Doc Watson is a great guitar player, but Scruggs style was based on the three finger banjo style, so it's got a different sound. And since Scruggs is primarily know as a banjo picker, it surprises some folks when they find out that he was a helluva guitar player.
He was also a big influence on early rock & roll.
BTW, bluegrass is one word.
Not in Kentucky. ;)
Actually, comparing bluegrass to rock is a bit unfair as the styles are completely different. If you really want fast, no one is second to Dennis Agajanian. One also has to consider Spanish Flamenco style as being a more difficult style to learn and play. Since this thread was about Hendrix, my comments were originally intended to be about Rock guitarists and not guitarists in general.