Recently, I began to experience typing pain in my right arm I couldn't ignore. It would extend from the pinky finger to the elbow in a line. I decided to take an interest in chording keyboards per my Russian acquaintance and purchase one, which I've now used for roughly half of the year; follows are the experiences I've had with it. In sum, I'm no longer using it, but it was a valuable experience.
I adjusted to using the chording keyboard within days, and heavily used it alongside my trackball; I noticed it was easier to use the trackball to recycle text when the words were long enough, and also noticed I wanted for nearly none of the complex commands Emacs provided me; the arrangement freed me from using any particular editor, and I also made changes to the environment to use the trackball in increasingly many situations. For the first time, I could type numbers without looking at the keys. Using the mouse more than I'd ever reminded me that I'm not using a true graphical operating system.
As looking at the chording keyboard provided nearly nothing, it was particular suited for data-entry tasks. When doing something which was almost, but not entirely so, dependent on mouse input, it was ideal. Even typing brief sequences of characters was nice, but the issues came with longer strings.
I couldn't type with it much and not feel issues throughout my left arm, but not my hand; unlike the right arm, it wasn't a line of pain, but soreness or tiredness which could extend to my back, and it sometimes became pain. I'm inclined to believe using the chording keyboard may have revealed issues with my posture and similar such things, but I don't truly know. Typing so slowly, and being unable to quickly issue complex chords some software demands had me feeling like an invalid at the machine. I also noticed the chording keyboard is particularly unpleasant for repeatedly issuing certain keys.
I've typed a great many characters with the chording keyboard by now, one document being longer than fifteen thousand, but the general trend was for my writing to become less frequent and more brief in all cases. The soreness in my left arm would sometimes cause me to cease typing for one or two days before resuming. At the least, my right hand was able to rest plenty during these experimentations.
After long enough, and considering I've two hands, I considered purchasing a right-handed variant of the keyboard, to use the pair together, and using a foot mouse, as even using a trackball managed to pain my right hand, at times. I decided perhaps the issue be that I'd never used a truly good model of keyboard, and have recently purchased a model using buckling springs, which is what I've used for typing this; I now feel little discomfort, even after using it for long sessions, and despite typing many thousands of key strokes with it often. Part of this may be my being careful not to contort my hands as I once did with a typical keyboard. It's a shame the chording keyboard wasn't any panacea.
I dislike acknowledging the best way to relieve typing pain: doing anything else; even physical work or playing a video game would relieve me. I found it particularly odd I could play video games, and never experience any pain; I believe it's due to the handheld nature of the device, allowing posture to change easily, but also that the controller simply is no precision data entry device; I correct a mistake, when using a keyboard, but correcting a mistake in a video game is known as getting better.
The chording keyboard could never be a total replacement anyway, as it's nearly useless for hacking; I successfully wrote some Ada programs with it, using the mouse to access template commands, but APL doesn't benefit from any improvement in typing, since the programs are already so small; that MMC of mine similarly doesn't benefit from a chording keyboard layout, because my design already reduces to the minimum any typing required. I didn't even try writing Lisp; I know it's wholly unsuited to it.
I believe I've learned from doing this. The chording keyboard revealed to me modes of usage unknown beforehand; I'm undecided as to whether it be more comfortable to hold it and trackball in my lap or at a desk. Previously, if I were with only one hand, I would've used a special layout for a typical keyboard, as this was that only solution for such I was aware of, but I now know this to be foolish.
I've seen the chording keyboard likened to a violin; I now believe there's very little violin music.
I'll certainly keep the chording keyboard around; if I were to ever lose a hand, preferably my right hand so that I needn't purchase another chording keyboard, I'll certainly resume regularly using it.