I had problems with tendonitis many years ago, and on top of that I was always fascinated with different input methodologies.
I used to work at HP which (although a corporation with no soul) has a great ergonomics program, so I tried just about every keyboard there is.
I tried all the simple contoured ergonomic keyboards such as the Microsoft Natural Keyboard (which was anything but) and it's likenesses, some good, some bad.
I entered the domain of the more radical, such as the Kinesis (inverted) keyboard (harder to get use to than you'd expect) and the Comfort Keyboard System which I stuck with for a while. You could say that I spent alot of time on the typing FAQ website (tifaq.org). I even bought a Twiddler which I want to train on some day..
Finally, though, I hit gold two companies later (at Transmeta), when a coworker let me borrow his DataHand keyboards. These things are wonderful - they completely eliminate wrist motion and finger stretch, and take very little work to operate.
I now use this keyboard fulltime and my tendonitis is gone (YMMV) and I get strange comments from anyone who sees my computer setup. (Admittedly I've noticed my knuckles now crack quite regularly - I think I need to stretch out my fingers more often).
It took about 2 months before I could type on them without getting frustrated, and about 6 months before I got close to my regular (flat) keyboard speeds - though at 100 w.a.m. I had quite a ways to go. Supposedly you can type faster on these than on a regular keyboard, which makes sense considering the simpler and smaller layout.
So, basically I love my DataHands and recommend them to anyone who wants a better input system or has RSI and is willing to commit the time to learning how to use them.
One problem is that they are a little more difficult to clean, so I setup a photo how-to for cleaning the DataHand
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