Anyway, back on topic... I think the kickdown switch is just another case of Germans over-engineering something. I've never driven a modern American or Janapese car that had one. Pretty much all cars with automatic transmissions built over the last 15 years have had throttle position sensors regardless of the throttle control (mechanical or drive by wire). A normal throttle position sensor should know when the pedal is fully depressed and then kickdown the transmission accordingly without the use of a secondary switch.

I have found, however, that after hitting the switch my transmission holds the lowest possible gear for a long period of time (sometimes too long IMO). I view it more as a "sport" mode button than a kickdown switch.