I agree with Ameesh and JimRaynor. It doesn't matter how much 'faster' dvorak is 'in theory.' In practice most people can type fast enough on qwerty to get along. Most of the time i spend on the computer is spent thinking, not typing. You'd waste many hours and weeks learning dvorak to get a few extra WPM. maybe if you were a secretary, working on a single computer, typing for eight hours a day, you'd be fine. It's like spending $10,000 to replace a fully-functional air conditioner to save $50 a month. Yea, you'll be a bit more efficient, but you will have wasted the equivalent of years of saving a few wpm/$ to improve slightly.
It's a neat idea when you think about. Then you realize that you can never really use another computer again....because you'd have to either use dvorak with qwerty key labels or switch back to qwerty. And forget about getting a dvorak keyboard on a laptop.