Unfortunately it only works with the scroll wheel, or scroll events on a trackpad. It works finger-crampingly slow with my scroll wheel, about 15 full seconds of constant action, but I just found a laptop to try it on, and I think I finally got the effect they were going for with trackpad scroll effect. Much smoother and a neat effect. Spoiled a bit by my first, finger-cramping impression, but otherwise smooth enough that if I stumbled onto that experience first I might have thought nothing of it, or even been impressed.

Still see no reason for it not to responded to normal navigation keys.