I've got a dom with quiet footsteps and it definitely makes some sort of difference. I've been right on top of unalerted people before they notice me, and had situations like this one where a guard that had come running to investigate my earlier gunfire and bodies and not found me (as I'd swiftly left the area and gone to loot the security datapoint) and with me making absolutely no effort to remain stealthy as I'd considered myself to have gone loud at that point, bust through a door to find the guy there with his back to me.I've got it on a dominator (no other mods, just bought it to test) and so not really suitable for "live demonstration" purposes. But I have a feeling it'll be quite useful in some situations on heists and sabotages where you're navigating restricted areas.
But the shorter range where NPCs will hear your footsteps isn't easy to gauge. I just think it should be "the same as crouch" (silent). It wouldn't break the game in any way and would just make the use of this mod simpler. As it is, one has no way of knowing the difference until tested out and then there's no simple way to measure that going forward, short of constantly looking at the radar. It's too risky, therefore, to use in many cases where it would have a positive impact.
I'd say "for professional use only" which is a bit restrictive. Even if I can master it, I can't say it's going to be worth promoting as a method worth investing practice in when crouch does the trick and is only marginally slower than jogging.
I'm pretty sure a normal suit would have turned around to the sound of footsteps at that distance, but this dude just didn't notice.