I've fitted a few of these electric tailgate kits, to Evoques and Range Rover Sports, not to a D4 yet though.
In all cases the owner of the car wanted the electric tailgate because one of their other cars had it, and so they missed having it in the LR.
It's a gimmick, sure, but you could say the same for reverse cameras, parking sensors, and other conveniences, once you are used to them they are sorely missed.
I put a reverse camera in my Mini Cooper S, not because i really needed it, but I got so used to having a camera in the other cars, I missed it.

