I wrote a while back about why typing on old keyboards feels better: it's because they were simple, low-latency devices interacting with your computer's bare metal. Nowadays, many device instructions end up filtered through a zillion layers of microcontrollers, firmware, virtual machinery, applications, hardware abstraction layers and God knows what else before a byte gets to the screen. How annoying is too annoying? is a Glitch site by Monica Dinculescu that lets you simulate keyboard latency, to see exactly how much of it you can take.
This is an experiment to see what amount of delay is too annoying for a user interaction like typing. Here are some presets; make sure to type a lot of characters at once for the full effect.
Note that whatever you select in the app, it's added to the actual latency of your own keyboard and computer–probably 100ms or so for most of us. After about 50ms of extra wait, I start to get aggravated.