I started learning Colemak about 3.5 years ago. I was already a pretty fast QWERTY typist, but since I was involved with lots of computer related work, I didn't want to injure my hands in the long run, considering I do lots of fine electronic work and play the piano and bass. Keeping my hands healthy is very important to me. I just went cold turkey, and after a week was up to a very usable speed. Since I would often be using computers that weren't my own, I would spend the first part of the morning on QWERTY so I wouldn't forget it. After a couple months, I was typing my typical 90 WPM on both layouts.

Now I switch between layouts effortlessly. I don't do the regular "Morning means QWERTY" anymore, but I use both layouts with most of my time spent using Colemak.

My only complaint would be using vim. I wanted to use vim so I could code with less time on the mouse (thus quicker and easier on the hands), but I couldn't get a decent Colemak layout for vim. There's one made by Shay, but I couldn't find any documentation or easy-read layouts which would have been helpful as a new vim user. I've since given up learning vim for now. Maybe later.

Just thought I'd let the internet know I am a Colemak user. I think I read somewhere that Shay estimates the number of users by multiplying the number of registered forum members by 5. So hey, I just "added" five users to Colemak ;)

EDIT: Just took a test on TypingTest.com using Colemak and got 116 WPM with 85% accuracy, for an adjusted speed of 99 WPM.