OK I know this is an old post, but I'll add my experience on the topic anyway. I started into windsurfing decades ago because I flew stunt kites and saw how much more fun was being had off the beach. Who knew what the future held?
My first advice: lose the directional and get a twin tip.
I switched over by taking lessons in South Padre, Texas with Brett at Air Padre; they use a boat and radio helmets and you can stand everywhere - he had me waterstarting the first day. It's more like wakeboarding than windsurfing, and the board skills are akin to snowboarding. The wind knowledge from windsurfing will help on an intuitive level, but once you're riding then it's kite handling, kite handling, kite handling.
Before starting I practiced with a stunt kite and watched videos and observed friends kiting and just went to the beach and asked lots of questions and listened. Also followed friends kiting in the swell in a kind of "monkey see monkey do" game; watched where they put the kite and how they varied bar pressure.
One point that I think kiters who've never sailed or windsurfed miss is that lessons tend not to teach you "the rules of the road", so I've seen too many instances where kiters heading at each other don't know which one should pass upwind, for example. Also who was taught that a kiter passing downwind should drop his kite and the upwind rider raise it? Beyond basic watercraft etiquette there are also kite movement and wave practices that aren't always imparted (Common sense isn't always common!), but initial lessons are key for basic safety (as kiting is inherently more dangerous than windsurfing).
Once you're confident with the kite and start getting bored with the twin tip then take the directional back out of the closet...