Dvorak on an IBM Model M.
Been using dvorak for ten years or so now... Using QWERTY for more than an hour or two a day hurts my wrists.
I can type 60+wpm in dvorak, upwards of 80 with caffeine. I get around 30-40wpm in QWERTY on a good day. I think the main difference is that I never learned touch typing on QWERTY -- I use a ninja-hunt-and-peck method, whereas in dvorak, you're pretty much forced to use a proper touch-typing method.
I've thought about learning colemak, I hear it's a lot faster and easier on the hands than even dvorak, but I haven't had the time to play around with it yet. A lot of the speed improvement of colemak is that the capslock key becomes backspace, so no reaching with your pinkie then finding home row again when you make mistakes.