I've been touch-typing for over 15 years (I'm 29), using a swiss german layout (QWERTZ) at first. A couple of years ago, soon after I became a student in computer science, I switched to QWERTY - giving up easy access to umlauts etc. but getting brackets, braces and slashes instead - which was handy for programming and work in the shell.
In december 2006 I almost switched to DVORAK, but decided against it because I was to start my first job (as a software engineer) a couple days later and didn't want to make a bad impression. ;)
BTW, I'm using Mac OS X at home (been a Mac-user forever) and got me one of those sleek new Apple keyboards last week. I'm also intrigued by keyboards with non-staggered keys, like the ones by typematrix.
According to a 3 minute test at typingtest.com ("enchanted typewriter") my net QWERTY speed was 72 wpm at 97% accuracy prior to switching.
Anyway, I found out about the colemak layout recently and was intrigued. Two days ago I made the switch (cold turkey so far). I did the first six lessons on that sunday (for about 3 hours I think), moving on as soon as I reached 97% accuracy. I was - and still am - very slow, little more than 10 wpm.
Yesterday I also used colemak at work (Windows XP and Mac OS X) - no programming ATM, but using Photoshop shortcuts and replying to emails was hard enough. Soooo slow. Did lesson 7 to 9 at home, again until at least 97% accuracy or a minimum of two passes per lesson.
Another slow day at work today, then lesson 10 to 12 at home. And now I'm posting this... :)
I like it so far and already noticed the potential comfort of using colemak. Though ATM typing anything requires my full concentration - when I just "let go" my fingers want to write QWERTY. ;) Oh well, I guess more time and training will help.