It really sucks that I type "Y" with my left hand's index finger. It makes a wide variety of interesting keyboard layouts infeasible without going in cold turkey.
For example, I went from a traditional keyboard to a Kinesis Maxim, which was a traditional layout but split. That required a bit of typing adjustment, like what you mention.
Then I switched to a Kinesis Classic (old version of the Advantage, PS/2 port). Now that was a pain, literally. Having to interrupt decade-old touch-typing muscle memory was annoying, and I actually experienced slightly increased pain (tendinitis) for the first several days.
Within two weeks, though, I was automatically using the new arrow key position and thumb keys (Ctrl, Alt, Home, End, PgUp, PgDn, Backspace, Delete, Enter, and Space) smoothly.
My change from QWERTY to Dvorak was even more troublesome and a bit painful. I would say it honestly took me about two weeks to become even barely functional, and a year to become completely proficient. I'm skeptical that I've ever hit the same WPM that I had on QWERTY, which I mastered while still an adolescent. Not that it matters, I just think a bit more and type a bit less now. :-)
Edit: for the record, I absolutely DO NOT advise learning Dvorak. Its ergonomic benefits pale compared to the mechanical keys, split wells, etc. Also, it means lots of key remapping for games, copy/paste shortcuts become kind of arbitrary, and so on. Stick with QWERTY, but use better keyboard hardware. Learn Colemak if you absolutely insist on the 1337-ness of 'superior' layouts.
I do agree about the time it takes to get all of your old speed back. When I learned Dvorak, it took me two years to get back to full speed. But once I was there, I was there, and with surprisingly little effort. I have a couple of victories on typing tests that I was actually trying to lose to prove it.
Nope. I still type Dvorak. One switch is enough.
I can type QWERTY, too. If I use a different machine, I'm able to switch over with surprisingly few errors. Also, strangely, I can't tell you where the keys are on a Dvorak layout without mentally typing the letter. I used to know the QWERTY layout by heart, but never reached the same level of mental mastery with Dvorak.
The only reason I suggest Colemak is that I've heard it's optimal for programming. I still don't think it's worth learning, though, if you already touch-type QWERTY.
But honestly once you get away from Qwerty there's a law of diminishing returns. The differences between non-Qwerty layouts are pretty miniscule compared to the difference between Qwerty and good layouts.
The problem with tendinitis, carpal tunnel, bulged neck discs, and health issues that afflict programmers is that you don't know you're susceptible until you already have the problem. Then you're looking at months or years to fix it and learn techniques and equipment to avoid its return.
I'll agree with you on the issues with key-rebinding for gaming and copy/paste becoming more difficult. Going back to typing Azerty/Qwerty becomes a real hurdle and this might be a problem depending on your situation.
But the pain (tendinitis or carpal, I did not check with a doctor) that I experienced after only 2 hours of typing disappeared completely. That being the goal of my change I consider the change a successful one.
I managed to learn Dvorak in 2 months, with the keyboard feeling more natural and logical during the learning period. While it took me years to become proficient with Azerty (the Belgian keyboard-standard). I accelerated my learning process with a simple CLI based typing-trainer.
TL;DR: Dvorak is more difficult in regular life but it can solve pain issues. So I recommend changing to the layout for that purpose.
*edit: spelling
I didn't have a negative experience with Dvorak, it's just virtually pointless when compared to the benefit of consistent, light key pressure, mechanical keys, and a physical design that suits your body.
Dvorak is more difficult in regular life but it can solve pain issues.
I don't believe this claim at all.
One common misconception is the idea that RSI is a single thing. It's really just a loose grouping of symptoms with a similar cause. So it's very common for a remedy to be very helpful for one person's RSI and do absolutely nothing for another person's instance of it.
For instance, switching layouts is more likely to bring relief for certain kinds of pain in the fingers, while changing keyboards is more likely to bring relief when the pain is in the wrists and forearms.
I just noticed I still use my left index finger to type "y" on a non-Kinesis keyboard. Strange.
Muscle memory is a weird thing.
Further, I did NOT use my Kinesis for eight years (it sat in its box after a move) and then I plugged it into a laptop the other day and... was astounded to find that I didn't even have to look at it to start typing immediately, even the thumb keys!