> I get how a power-user like myself might struggle to switch (if anything goes wrong with the Linux box, it will be dear husband who has to deal with it!), but what's wrong with Linux for a super-casual user who basically just needs a browser?
Pretty much this.
I originally installed Ubuntu for my parents when I first got them a computer separate from mine. All they needed were things like the browser, preconfigured email, instant messaging, possibly a word processor, and a way to look at their photos. They didn't need to know how to configure or install anything new. As a bit of a caveat, I think I always did the importing of photos from their camera for them. But I don't think the difficulty of that is necessarily very OS-dependent.
I later switched them over to Windows at my father's request when replacing the (by then) ancient hardware with a new laptop that had Windows preinstalled. But I don't think it really made any difference because they still didn't do anything requiring more than opening existing apps.
But if you're used to knowing how to install new stuff and how to configure things to your liking, yet don't want to learn how to do those things on Linux for the sake of it, I can imagine it being hard.
With that said, of course a different desktop can also be and look unfamiliar even if there's little practical difference. And for some people near-exact familiarity can be rather important.