I learned Colemak, for fun, really. There were several very distinct phases.

In the very beginning, just hitting the right keys most of the time was very challenging. I'd have to actively think about where to put my fingers for a few days or up to a week. I did a lot of training exercises then.

After that, I was able to type pretty good at 20-30wpm, growing quickly. I played lots of type racing games.

Until I hit about 70wpm again (I started at QWERTY with around 100-120wpm, depending on text types), it was super frustrating, because I couldn't type fast enough to keep up with my thoughts. I would feel my thoughts slip away as I was still typing the last thought out, thinking "Wait, nooo, I'm almost there!"

I think it took about a month or two until I hit 70wpm again.

After that I felt like it was usable and I could probably be productive in it.

Oh yea, I should mention that I was on a sabbatical during that time and did the Colemak switch full-time, cold turkey - I haven't typed in QWERTY since except when some stupid 3rd party computer doesn't have Colemak (it comes with every modern operating system) and I have to use that for a second. But because I was on a sabbatical, I didn't need to be productive for months. It would've taken me 1-2 months to be productive enough to write code or respond to emails/chat quickly. Colemak is very coder-friendly in that it doesn't change any of the special characters except ";" and the zxc keys are all the same.

After reaching the 70wpm point, it was mostly smooth sailing, but I wasn't 100% yet. I'm a vim user, so a lot of my muscle memory was wrong. I simply continued using vim as usual and ended up learning the hjkl keys on Colemak. They're actually all under the left index finger, but spread around in a weird way. I'd have to look at the keyboard to tell you what they are, but my fingers know them.

So, eventually, vim and everything is just fine. Also eventually, I got back up to my old speeds of about 100-120wpm, again depending on text. I've read that Colemak is actually not as fast as QWERTY because it optimizes for low finger movement, not speed. While I think it'd be cool to type 150wpm, I don't really miss it except when doing type racing games. I seem to think somewhere between 70-100wpm at most. My fingers move a lot less when typing than using QWERTY, and people have commented over the years on that.

Another thing that took almost 2 years to go away was "awkward angles." You know how some people who learned touch typing can't use the keyboard except when their hands are exactly aligned with the keyboard? I had that. So sometimes I would try to reach over to my laptop and hit the pause button, or mute, or something like that, and just have no clue where to press, because I only had that knowledge in relation to my index fingers being on the home row. I'll admit that this is pretty unimportant, but I just used to know that by heart, no matter the angle. I've since learned the Colemak positions for most of these, probably just from doing it and getting it wrong for years on end ;)

By the way, as part of this, I also reconfigured my default movement keys for video games. Why are people using WASD? Much too close together. I use EADF, so I can play video games with my fingers on the home row in normal position. Much more comfortable than WASD.

Programming keys/symbols were never an issue on Colemak because most of the symbols stay the same. Only ; changes position, and ; is useless and languages that use is except as comments should go back to the 7th century where they belong. C can stay.

I've met several Colemak typists who are able to fluently switch back and forth between Colemak and QWERTY, and one even also Dvorak. I had a hardware-switched Colemak keyboard at work and this new guy shows up. He types for a second, looks at the screen (git add == dug ass in Colemak), and begins typing in perfect Colemak. Wow!

I seem to have completely lost my muscle memory for QWERTY. Maybe it would come back if I tried using QWERTY, or switching between the layouts regularly. But I don't have to ever use QWERTY, so I haven't even tried.

Colemak has the advantage that, as the third most popular layout, there are off-the-shelf keyboards with hardware switches for it. I never got into building/modding my own keyboards, so I just got some random Taiwanese mechanical keyboard that offered a Colemak switch on the back. There are several, all I've tried were very good quality and fun to type on. Dvorak is even more widely available, of course.

Was it worth it? Hard to say. You kind of have to switch layout on every computer you use, e.g. at work, or bring your own keyboard. But I bring my own keyboard anyway, so that's not much of a difference. And Colemak comes with Linux and OS X, and probably on Windows too. So it's really just a few clicks away.

I'm not a faster typist. I didn't have RSI or any other wrist pain. Maybe I would've gotten it and now I haven't. Maybe I'll get it later than on QWERTY. It's a bit of a hassle when you get a new job or have to use your co-worker's computer. Everybody finds it very fascinating and wants to talk about it for exactly 30 seconds, then never hear of it again. It is hilarious to have people type "git add" on your Colemak keyboard.

I was just bored on my sabbatical. I don't think it makes a huge difference. If you have RSI issues, like I see people post here on HN all the time, go for it. I've also never bothered to get an ergonomic keyboard, but for some people it makes a huge difference in their typing ergonomics or strain. If you have issues, you can definitely give Colemak a try. But don't expect any huge productivity boosts.