mmmmm ... I DO like the idea of keeping a constant favourite cadence with variable road speed ... especially when setting off around town.

But I just cant see that without any positive transmission (ie just friction into / out of balls) that the efficiency will be same as regular hub gears (which are already a bit inefficent in non-direct ratios.

But like Jur, I am fascinated, and cant wait to try it in anger, (not just in the shop).