I bought the Datahand and used it for a good two weeks. The mouse cursor can only be controlled up/down , left/right with it. With too much graphical work, that cut my use of it short.
Several years later I started a strength training program, and within a few weeks my RSI vanished. At its worst, my arms would be numb when I woke up, I had sustained numbness in one hand for weeks, at one point I couldn't physically hold a mouse more than 15 minutes. It took a quick Google Image search to know I would never do a carpel tunnel release surgery.
After adding up the workout time spent, it was about 4 hours of strength training (no weights or gripping) that ended 5 years of debilitating wrist pain. From what I've been able to tell many years later, it was all from doing pushups -- which likely has everything to do with shoulder and back muscles. That ironic thing was, because the pain was in my wrists and arms, I thought doing pushups would cause too much pain so I had stopped doing them.
Now instead of ergonomics I think of how to be more active while and between working.