Sure, it's a way to go as fast as you'd ever want. (The world record is over 55 mph.)
But for must of us it's not really about raw straight line speed. On a good day your mind and body cooperate tightly together, simultaneously responding to wind and waves that are shifting every second. You're embedded in this environment, where every twitch matters. When it all comes together, zen-like, you become one with nature.
As with anything worthwhile in life, you'll always be learning. No matter how accomplished you are the next maneuver you've never done is the hardest, and uncommon amounts of effort and frustration are always part of getting there. That makes it all the more gratifying when you at last succeed.
While you may find some valuable advice here, nothing beats eagerness and lots of practice, as well as watching and studying more advanced windsurfers.