Another anecdata. I had a bike accident which took my left hand out of commission for a while. It was after the Matias keyboard became so expensive, and I was broke. But I was motivated enough to try the concept that I hacked together a software implementation that behaved more or less the same way on a standard full size keyboard by swapping to a mirrored system keyboard layout while holding the spacebar for a short time.

The software itself was buggy as hell (I learned just enough ObjC to get it kinda working), but even so the mirroring concept worked perfectly for me. It was basically no learning curve (full QWERTY to half QWERTY), and I only took a slight hit to typing speed. The first thing I did was prove it out by building another bit of software to relaunch the first whenever it crashed, and then worked full time with it for a couple months. Typing was never quite as subconscious for me as it is with both hands, but it was as close to that as I could imagine.