I've been typing Dvorak since age 17, so... 37 years. Despite breaking my left hand (not while typing) I haven't lost any typing skill/speed that I can tell, and I haven't ever seen a hint of carpal tunnel syndrome.
Btw there are dvorak layouts for one-handed typing, both for left and right hand. If I ever break my arm so I won't be able to type for some time, I'll definitely try that.
