In the case of playing guitar... speed is a novelty. I find it more interesting to watch Rusty Cooley play than to sit down and listen to one of his songs. Speed doesn't make you a better guitar player. Someone mentioned how its similar to how fast people can run... Being a fast runner helps you in more ways than one... stealing bases in baseball, getting up and down a basketball court, running for a touchdown, 100m sprint, running from the cops.... etc... In guitar it just means that you can play faster than most people. Speed is a novelty...