Just got my MayFlash Wii U Pro USB adapter and am mostly happy with how well it works.
In Xinput mode, everything mostly works, but I am not able to sync more than one controller and I also cannot map the ZL/ZR buttons. I also run into some weirdness because + maps to Menu and I tend to use that for Start in emulators and it causes the menu to pop up all the time. - maps to back, but I think most emulators are smart enough to ignore the back button, so that doesn't really cause any issues.
In Dinput mode, I'm able to sync multiple Pro controllers, am able to map ZL/ZR, and the + and - buttons actually map to gamepad buttons, rather than Android navigational buttons. The issues with Dinput mode are that I can't map the analog sticks at all and the controller can't be used to control the FTV at all.
If I could get the analog sticks working in Dinput mode, I'd be completely happy with this purchase, but as of now I need to choose between one player games with the analog sticks, or two player games with the dpads. Anyone know what it would take to get the analog sticks working in Dinput mode?
EDIT: URL for the adapter is http://www.amazon.com/Wireless-Wii-P.../dp/B00E6553PW
. You just plug it in to the FTV's USB port, hit the sync button, then hit the sync button your Pro controller and you're good to go.