I'm using a type-II (German) Dvorak with some custom modifications that map [({&#60;})]&#62; to Alt Gr+homerow (Linux)/Alt+homerow (Mac) and the caps lock key to Alt Gr and Alt, respectively. I switched for ergonomics (big improvement, no RSI pain at all) not speed; if my speed has improved, it's probably not by much, but then I don't think I've ever wished for faster typing speed.