The best ergonomic keyboards on the market.
slate.com
slate.com
The best bit is the placement of the non-alphanumeric keys e.g. space, enter, delete, backspace, ctrl, alt, etc. They are all placed in those two clumps under each of your thumbs where a traditional long space bar would be.
It also has arrow keys arranged in a Vim-like JKLH arrangement just below the "normal" keys.
I also type Dvorak on it and I can configure that within the keyboard software rather than in the OS, not that that's particularly hard but it's nice to plug and go. (I don't have the slightly more expensive Dvorak keycaps model they sell because if you're looking at the keys then you're doing it wrong)
Every time I've had a question about one of mine, they give me great support. They're sturdy and well-engineered -- no disposable-age manufacturing shortcuts. I own two, and I'll take them with me to the grave.
For many years I have been an enthusiastic user of the Happy Hacking keyboard:
http://en.wikipedia.org/wiki/Happy_Hacking_Keyboard
Not to sound like an infomercial, but it fixed all my hand/wrist pain problems. The other advice I received, which also helps after that too-long playstation session, is to sleep with your hands straight (wrist unbent, fingers uncurled).
I've always wondered about that AccuKey though.
Chording is a nice idea, could be brilliant if wrapped around the edge of a phone/PDA (e.g. http://www.xaphoon.com/dataegg/ ) but is too slow to be an everyday desktop keyboard replacement. Less comfortable than normal typing, as you use many fingers per character instead of just one. Even if you're one handed it's probably still faster to type on a normal keyboard.
As the CyKey goes, it has a bit of a classic Spectrum rubber keyboard feel, not much feedback.
Don't splash out just to try the idea, I've just cobbled together some Python/TKinter that you can play with here:
It's a text box and you can chord using the right arrow key along with the numeric keypad keys 4/6/8/enter (I find them a pretty good fit for my fingers).
The chords are here: http://megasharp.com/cykey.asp (plus "thumb" on its own for space).
There are many more in the CyKey system for numbers, punctuation, shifting, control keys and so on, but a) I don't know what they are, and b) it's freaking patented/copyrighted so I oughtn't even use these few.