I changed to the Colemak format way back in 2006. Forced by necessity as I had destroyed my hands and arms with the QWERTY format.
I've been a touch-typist since the early 70s when I did typing at school for 2 years (and hated it!). But when computers came along it quickly proved to be a godsend.
From about 96 through to 2006 I struggled with RSI problems. Used voice systems with some success. But finally made the call to change the keyboard layout.
My first attempt was with DVORAK, that seemed like the obvious one to change to. It only took a few days to realise that it was going to be great on my left hand, while my right got overloaded. Scratched that and went back to QWERTY.
Months later when idly scanning around for alternatives (not many back then) and Colemak popped up in the search results. As a heavy programmer and text generator the ideas behind Colemak appealed so I decided to take it on.
It only took a few days to remember the key positions without the need for the layout pinned to the wall. But it did take months to become completely fluent.
To me, fluent means being able to think of a word/phrase/"programming construct" and just have it appear on-screen without any conscious thought about typing.
I've been using Colemak since and without a doubt it has been a big contributor to the rehabilitation of my hands and arms. I'm still doing fundamentally the same job of code and text and I believe strongly that I would have have been forced give up my career years ago if I'd stayed with QWERTY.
I may be unusual, but I did find that I can only be fluent in one keyboard layout at a time. So Colemak destroyed my QWERTY typing. Nuisance value when I'm working on client systems. In response I've developed the technique where normal Colemak typing happens when I'm looking at the screen. QWERTY typing I have to look at the keyboard. Big incentive to put the portable Colemak utility on all the client systems that I work on!
It was a big boon to me when IOS released the Colemak layout for iPhones and iPads. It makes no difference to the on-screen keyboard, but any blue-tooth connected keyboard uses the Colemak layout on all my devices.
Well worth the change over from QWERTY. I would also recommend that anybody wanting to start touch-typing should start on Colemak from the beginning.
These days the only RSI problems that I have trouble with are mouse induced. There has got to be a better way of pointing.... Any creative ideas?