I had a Touchstream for about a year. The gesture support was amazing, but typing on it without tactile feedback was way too difficult. I eventually got to maybe 60-70% of my typing speed, but it took a lot of concentration. Sure, having the gestures available anywhere saved some switching back and forth form the keyboard to a mouse/trackpad, but overall, except for casual usage, it wasn't workable -- certainly not for someone who writes code for a living.

Some people on the forums claimed to get close to their old typing speed, but I have to think that they were folks who didn't type that fast to begin with, or who had more severe RSI / handicaps that made conventional typing too difficult. For someone with only minor RSI or who types in the 50wpm or higher range, I can't see how it would be a net positive.

It'll be interesting to see if Apple ever tries to reincarnate the idea in some form or another -- there have been rumors to that effect, but none I'd call reliable.