Figured I'd share my experience since I found others' useful.
A week ago today I started learning the Colemak layout, mostly because it looked interesting. I gave Dvorak a very brief go many moons ago, but it was just too brutal. When I saw that one of the benefits of Colemak was the easier learning curve, that definitely peeked my interest. Note that I was a very fast Qwerty typist though, I never really learned to type "properly" but I tested at 118 wpm immediately before starting.
I program all day so really couldn't afford the productivity hit of going cold turkey so decided to study Colemak at night and continue as normal during the day. I used the most excellent Type Fu and it's built in Colemak progression to learn the top two rows, which I completed on Friday (a total of 10 progressions of two keys each, leveling up at 40wpm at each). The bottom row was so similar that I didn't really need to study it. Starting yesterday I switched my computer to Colemak full time and while painful I think next week will be ok.
I currently have a 35 wpm average on TypeRacer, which is a good deal slower than I do in TypeFu but I think that is mostly a matter of retraining the brain to use Colemak everywhere not just in TypeFu. During the week I wasn't having much trouble switching back and forth, but now that I've gone full bore I am already having trouble typing in Qwerty. I will admit that is a bit scary, but I think 50 wpm is not so far off and after that I think working will feel bearable.
On the layout itself, obviously I really like it. Though I doubt I will exceed my previous typing speed, it seems like getting into the 90s is attainable in a few months and I gather it will be a lot more comfortable. Overall I've kind of enjoyed the experience of retraining something that has been so ingrained in my brain for the last 30 years and overall surprised it hasn't been even harder.
I'll try to post weekly updates over the next month to share how its been going, but I'd say if you are on the fence then it is certainly worth a go if you want to challenge and experience something different.
Cheers,
Nic