There are two regularly occurring situations times where I'm delayed by the slowness of interfaces:
1. At work, waiting for our web app to reload after I've made some changes to the source. This is actually a problem and eats up a significant amount of time and makes me lose focus.
2. I'll occasionally come across a slowly loading webpage. And I stress 'occasional' here—it's maybe once every couple of days when I open an article on HN or something and it's some site with a tons of ads and stuff. It's a non-issue—easily less than 5 minutes per week.
Aside from those delays, I basically never find myself waiting for whatever software interface I'm interacting with, and that's on a 2014 macbook pro.