I've had a shot at it.
I actually have my keyboard keys rearranged in DVORAK right now, but Windows still has it layed out as QWERTY.
It makes it alot easier to learn when you can look down at the keyboard to find that elusive key that isn't in the spot you thought it was.
I got fairly decent at DVORAK, doing some online tests for speed and accuracy, but about a month after I stopped, I forgot it all.
It's great having my keyboard keys rearranged, though. If anyone tries to use my PC (living in a dorm, roomates, etc, are always trying to), then they get so confused and give up.
I'm a bit like Hyrichter in the sense that I rarely look at the keyboard even for numpad, or Home/Del, etc. I know exactly where all the keys are, so there's no point looking