Low-latency UIs that respect user input are amazing. They're just quite rare these days. I guarantee the difference is noticeable and makes a difference—look at how everyone liked (and still likes) the UI smoothness and low UI latency of iOS, for example, and iOS, though probably the current front runner on this front for popular operating systems, is just so-so at it.

I guess if my principle is that I like my computer to respond quickly and accurately to my input then yeah, I dislike webtech junk on principle.

[EDIT] as far as it not mattering, everyone I know, including plenty of non-techies, who has used Google Docs hates it, due to the UI lag. Typing with that large a delay between keypress and the letter appearing sucks. They may use it anyway because they have to, but they all complain about how laggy the UI is, responding to clicks and keypresses.