Tried one of these at the main IEE/IBC Broadcast show in Amsterdam about 2 years ago: if you can touch type and made very distinct, medium speed typing strokes it was excellent. If you speed up, get sloppy, it starts to lose its grip. Also, you cannot do "chording" with the shift key very well, and if for any reason your typing patterns "cross over" the line of sight of the sensor, it drops keystrokes.

Superb bit of technology. Give it a bit of time - they may have improved it a lot since then. There were a lot of people queuing to try it out at the time. Definite 10* geek quality.