a10a7f53_DvorakHowTo___Some_Wiki__Reason
[My Experience] My QWERTY speed was about 80-90 wpm; current Dvorak speed is about 120-130 wpm. [Reason] 
You are likely to see a typing speed increase on the order of 20% or so (a number that may vary wildly depending on what your initial QWERTY speed is: if you start out a slow hunt-and-pecker, you could see 100% or more, if you started out with 100 wpm, you may get something as low as 0-10%).
DvorakHowTo - Some Wiki
Reason