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.