I actually demo'd one a long time ago. It was a Christini bike but obviously not electric. I think it was either at a Jorbafest event, 24-Hours of Allamuchy, or Mountain Man at Mahlon Dickerson. I thought although it was interesting, I saw no real benefits because the power and torque was distributed evenly (mostly) between the front and rear wheels all the time. There may be some loss of power to torque to the front due to the flexible drive shaft but not enough to make a difference. So most of the time all that energy going to the front is not needed or desired in a full analog fixed system. Now, on an ebike using a front hub motor and a controller with some brains, power and torque to the front can be delivered at will only when and where it is needed is a totally different story. Imagine a front wheel pulling you out of a turn on a berm? Also, having a hub motor will allow for a full suspension bike because no drive shaft.