Hah, I can mention latency again!

I had the Amiga, 68000 at 7.09 MHz (PAL, NTSC ran a teeny bit faster). Both Mac and Amiga gave fully featured, incredibly low latency GUIs. They might think a bit after the click, but compared to a modern GUI, oh so snappy.

Windows, OSX, X with whatever Windowing never get close to that instant tip of your fingers response. I miss low latency responses.

Well, I wouldn't make such a categorical statement about latency. I remember an early Amiga word processor that had an unbelievably laggy and slow UI, such that it was basically unusable.

The Mac mouse pointer was always responsive due to interrupts, but that didn't mean that what you clicked on was.

However, the thing that I hate most about the modern web and similar UIs is that they reflow or otherwise move the content you are looking at after you click and before the click is mapped to an element, so you don't get what you click or tap on. This is absolutely unforgivable in my opinion, and absolutely not a matter of degree or grey areas unlike most of the things people complain about.

Amiga's pointer was a hardware sprite, so that always stayed responsive. Was more thinking of the OS's themselves rather than within applications. You could certainly get Amiga to slow down in the apps, particularly if you were programming it badly. As it generally only redrew when needed and managed layers and viewports pretty well, getting it that laggy would have taken effort. :)

Took years after I abandoned the platform for serious use for Windows not to always be more sluggish, and get dramatically worse when under load. Course by then I was on '040 comparing with Pentium something.

Definitely could be poorly written exceptions. There is a good post here describing keyboard latency on old computers.

https://danluu.com/keyboard-latency/

This is especially egregious on mobile because it's much harder to point at anything accurately with your finger.