I was VERY right-handed. I work as a computer programmer, and one day I felt deep throbbing pains stabbing their way from my hand all the way to mid-forearm. These pains were so bad, I immediately began using my mouse left-handed. I began using my left hand as much as possible, and the pain in my right arm went away. I eventually switched to a Microsoft Natural Keyboard Elite. The keyboard that curves. When I went back to using my mouse right-handed, the pain did not return. The curved keyboard did the trick. I am not using my left hand as much as I was, but it was gratifying to learn I could learn to use it more often if I wanted to.