Not yet!
but I think I want one on my bike to clean up the front end.
I aint no engineer, but it looks like it should have all the same braking power as a larger rotor. the force needed to stop a bike that close to the axle has to be far greater than an 11" or 13" rotor. but with the friction material all the way 'round the hub, it should make up some of the difference. Hydraulics are amazing; with the right combo of master and slave, alot can be achieved. (Just look at the pyramids) ha ha