I type in dvorak, and the differences i have noticed between dvorak and qwerty, is that qwerty has the fingers you use, bouncing between your right and left hands in between
every letter you type. Dvorak has your fingers bouncing between your left and right hand after
every 2 letters(not in every case, but more often than not).
This being said, Dvorak has proven to be easier for me to type on a full sized keyboard, but more difficult on my iphone. I'm jailbroken, so after seeing this thread i downloaded the dvorak keyboard, and found it to be slower, due to the fact that your left thumb would hit 2 letters, followed by your right thumb hitting 2, and back and forth, and that is taxing on your overall speed.
Most importantly however, it's not my job as a consumer to decide what is best for people, some people might like dvorak on the iphone, it would certainly be nice to have that option without having to install 3rd party, non-supported software.
But all research aside, I like dvorak on my computer better