I have been using qwerty layout since 1980. Oh dear, that's 37 years ...
I remember looking at Dvorak years ago but it never seemed worth the trouble. I heard about Colemak about six months ago and it got me thinking. Eventually I decided to give it a go. I started last Friday, the 21st of April. I started to change the layout for some applications but not all, as my typing dropped 40+ wpm. I have to run Windows at work and Linux at home. During the weekend I used only Colemak, so at work today I decided to go all in and use Colemak all day.
I use 10fastfingers.com to measure my progress and to compare if and how my qwerty typing will decline. I'm not that happy with 10fastfinger as it's just random words. When typing normally it's much faster as I know what to write instead of having to read it first and type the same thing. But I will stay with it as I can test both English and Swedish. So far I type about 56 wpm in English and 64 wpm in Swedish using qwerty. Three days ago I dropped to 8 wpm in English and 12 wpm in Swedish using Colemak. Today I had the same speed in qwerty but an average of 13-15 wpm in Colemak. Interesting that in Colemak I didn't see any difference between English or Swedish today. I thought it would be hard with the Swedish characters but turned out it wasn't.
I also had some fears about using Vim, which I do a lot, but it was a quick transition from the Swedish qwerty layout to a standard US Colemak layout. No need to rearrange keys.
I printed the keyboard layout, taped to my screen, but only had to check it the first couple of days. Now I just need to get that muscle memory going to get the speed up!