I don't think switching to Dvorak is worthwhile. Most people don't have the capacity to actually squeeze out the few extra wpm that Dvorak gives you, and if you do, the benefits aren't extraordinary. Plus if you use Vim, either you'll have to remember where the original keys were on the keyboard and use it solely through muscle memory, or relearn.
To me (Dvorak typist for > 2 years), it's not about increased wpm. I'm actually not a fast typist. It's about greater comfort at the keyboard, because ~70% of my keypresses are along the home row, compared to ~30% with QWERTY.
WRT Vim, I made the switch without too much trouble. In fact, I find the j/k on the left hand and h/l on the right hand useful.
And most of us are programmers, right? Beyond some very low threshold I can not imagine WPM factors into programmer productivity. If you are a writer then perhaps it would help.
Luckily I began the transition to Dvorak before I ever heard of Vim. The process definitely would have proved more painful with an additional set of muscle memory to override.
