I've just been testing the Xiongda 2-speed hub-motor. It works perfectly, though a little noisy. As far as I can figure out without opening it, it changes speed by reversing direction. It's fully automatic. It cuts the power for half a second to change gear. I'm very impressed by the way they pulled that off. It works much better with 12S lipos, and can go up a 14% hill without pedalling and with a total weight of about 130kg. It's about 150mm wide with a seven speed DNP free-wheel on it, so I had to stretch the frame a bit to fit it in. Weight is 3.3kg, and it's the same size as a Bafang QSWXK5
Compared to a Q100:
Controller looks pretty normal, and is about as small as they come:
I wrote a bit more about it on Pedelecs forum:
http://www.pedelecs.co.uk/forum/threads/xiongda-two-speed-motor.17219/