Overall: Even for someone picky about lag (like me), this adapter is perfectly fine. The stick feels 1:1 to N64 on MQ, haven't tried other mappings. Build quality is not a problem. C buttons are mapped entirely to C-Stick, so Melee jumping does not play like 64. Control stick range outside of Zelda is pitiful on every setting. Do not use as a general-use adapter.
With L and R you can select analog stick mappings comparable to the Raphnet adapter (just a linear conversion). R option is more sensitive.
I might have an idea how to add reprogrammability of button mapping. I might add it into the firmware. The button mapping needs to be programmed with a programmer, but if you can select from a few profiles that should be an improvement regardless.
Edit: hrmm, or make a Wii app that enables it. Not sure if that would be possible.. I would need to see if I can somehow send a signature to the adapter, so it goes into reprogramming mode.