I do the vast majority of my shopping on Amazon or other online sites. The only place I really buy stuff from in person are the grocery and the pharmacy so my experience with self-checkout in the last 10 years or so is limited. I don't do it at the grocery because it's always a bunch of stuff for the weekly groceries and there is no self-checkout for prescription drugs. And the closer grocery I go to for a few items at a time doesn't have self-checkout.
I'm sure there are places it works well, and I recall it working okay at Home Depot, but most of the places I go now it's not really an option.