To the touchpad on the back:
Wii controls were also weird when I saw them first. Also the Dual Analog concept was weird in the beginnig especially because in the 32 Bit era games didnt used it in a good way.
Maybe this touchpad on the back turns out to be super convinient. Who knows what they are going to do with it. Once the game programmers figure out a good way to use it,it could turn out to be as essential as a second analogue stick.