My TouchStream Input Device showed up while I was in California. I fiddled with it on my Linux laptop for an evening (Linux's USB drivers recognized it with no fuss, but I had to do some esoteric editing of my XF86Config file to get the mousing function to work under X), then took it to work Monday and plugged it into my desktop machine there. I've been using it every day at work.
It indeed GREATLY removes the stress on my fingers and wrists, and I feel much less stressed and sore after a day of working on it. Mostly this is because there is much less wrist-twisting and long reaching to do, since they did a good job of converting the most common wrist-abusing motions (the long stretch to the backspace key, awkward control-alt-meta-multishift sequences) into multi-finger gestures done either on the home row or just above it. Even the worst of these, the control modifier, is just a stretched-out chord using three fingers and thumb.
Many of the odd things about using it, such as the split space/backspace areas, the home-row-shift, and the unique way I'm gesturing the "enter" key, got stuck into my head VERY quickly. I was amazed that within just two days, I was shifting with four fingers and pressing return with six, and not thinking about it at all.
What IS causing a lot of trouble is the annoying way that the letter keypads are lined up directly underneath one another, instead of being slightly offset as on a regular keyboard. As a long-time touch typist, this is really really hard to get used to. If my left middle finger rests on "D", then "C" should be below and slightly to the center, or as my much-grooved muscle memory knows, exactly... THERE. I hit these keys without thinking about where they are at all... except they're not there, exactly. I wind up striking between C and V, and V and B, a lot. Ditto with U, I, and O. The device does have a built-in dictionary so that if it catches me striking BETWEEN two keypads, it will make a pretty good guess as to which one I meant. But if I squarely strike the wrong one, it assumes I know what I'm doing and does not make a correction. And of course that helps not at all when typing, say, router config language instead of English. Fingerworks claims they had a good reason for lining up the pads the way they did, and they even explained it, but it didn't make much sense to me and makes even less sense now that I'm trying to type on the thing. I suppose I will get the hang of it over time, but this is the single most frustrating part of the whole affair.
The mousing, dragging, and text-cursor control gestures are a breeze to use and make editing so easy that it's practically a work of genius.
Most control-alt and control-shift key combinations are unnecessary since there is usually a simpler gesture for them, but when there isn't, multiple modifier keys are kind of a pain. One is tempted to press, say, control and shift at the same time, then strike the key, just as on a normal keyboard, but of course it sees hitting two keys at the same time as a gesture (mousing, in this case), so instead you have to make this rather deliberate motion of control, then shift, then the key. Slightly annoying but I don't have to do this often.
I was touch-typing (except for that annoying keypad placement issue) within a few hours, and while I can see my speed and accuracy slowly improving, I totally believe them when they say it'll take weeks to get back to my usual speed.
I love how small this thing is on my desk when compared to a regular 105-key keyboard plus mousepad and mouse to the side. I have room for a coffee cup and Palm pilot in addition to the keyboard.
My bottom line so far (would that be a "subtotal"??) is that this is a very well-functioning device for which a tremendous amount of thought and design was done to get it to be operationally as well as ergonomically superior to traditional mechanical input devices. It is NOT easy to learn, and takes considerable committment to gain competence, but the returns in the end seem like they'll be more than worth the investment.