Dunno about mobile and perception, but IME, most piano players can tell difference between 20ms and 10ms latency between pressing a key and hearing a sound from a software synth.

and yet, just registering the keyboard press mechanically will give you a much wider range of varying latencies depending on how fast or slow you press. To recognize velocity, there is a switch at the top (near the hinge), and a switch at the bottom. The timing difference, which can amount to up to 200 ms, makes up the velocity. This has always confused me, on the one hand, you spend your time tweaking IO audio buffer to have the smallest latency possible, and then you would have this input device introducing "enormous" latencies, and have them varying too.

Are you certain that is how velocity is registered?

I mean, you could be right for all I know, but I own a number of devices (drum pads, specifically) which register velocity but which don't require that kind of latency to create the information; I don't see why or how that would be the case in most keyboard controllers.

Thats interesting. But its sound vs vision.