[gameswithgo]

You may not notice, that doesn't mean nobody does. Also it can depend on your operating system. Windows 10 (maybe everything now?) forces you to be in vsync, so increasing refresh rate has a non trivial improvement on the # of ms for a keypress response.

Now whether you will notice that can depend what environment you are in. If your editor already has an input latency of 100ms then shaving 8 off probably is not noticeable. But going from 20 to 12 might be.

[folmar]

Definitely not everything. Non-compositing window managers on Linux (non-wayland of course) work in the old way.

[westwing]

On Windows 10, and I have tested various text input boxes. There's no way latency is anywhere near 100ms, I would notice that.

Generally, from the tests I've seen, input latency is 30-40ms on a wired keyboard on Windows.

[VRay]

you can just point a phone camera at the keyboard and screen, record a video clip, blow it up into stills with ffmpeg, and then count frames

Even at 60fps, you should be able to see the difference between 30ms and 100ms. Newer phone cameras often have a "slow motion" mode that'll give you 120+ fps video, too

SOME people can see the difference between 30ms and 100ms, but it's almost impossible to actually see it. You'll mostly end up feeling that everything sucks and not knowing how or why.