I paired it with an Xbox One X pad (original Xbox one pads don't work, needs to be S or X pad) as well as an android Ouya pad. I spoke to the guy who made it and he is now working on a driver for the WiiU Pro pads too.
It works pretty flawlessly and you can easily swap between port one and port 2 as well as use 2 pads, one for each port. Auto fire is supported as is both the D pad as well as analogue stick. As it comes it expects 5v from an external source but I am going to test mine pulling 5v from the joystick lines. I will report success if if that works.
It works. I soldered the 5v line from both joyports together and connected that to the 5v input after the diode (it's not needed as you know its the right polarity and the voltage drop wouldn't help matters). If you assemble your own you can miss the DC jack and the diode out completely and just connect the 5v pin to the two joyports on pin 7.
Fun to play games with a Bluetooth pad on the 128!