I rode one in the early 90s at a bike trade show in Long Beach. Very smooth, given I was riding on the convention center floor. As an engineer I had a deeply visceral response to it. If I had one I'd strip off the parts and hang the frame on the wall over my fireplace. I looked into them here on BF a few years ago and found they had serious problems with cracking after short periods of use. Really the were all prototypes. All made in one size in one gigantic die-cast mold. Refining the design would cost another half million for another mold with each redesign. Modern software would help.