I'm a few hours into dabbling with colemak using the TypeFaster program under WinXP. I became interested when I was reading an article about dvorak and saw colemak mentioned and thought I'd give it a try... so far it's been good, but very frustrating - this was to be expected though.
I've never tried anything outside of qwerty before and I'm not the greatest typist in the world to begin with, I can sustain no more than 65 wpm with qwerty for a period of an hour. Right now I'm hovering around a whopping 17 wpm with colemak but I'm hoping that improves with time.