[EDIT] Oh and there was that release in the late '00s, I think, when they pushed out PulseAudio way too early (shoulda never done it at all...) and it caused your whole X session to crash if your browser loaded any Flash content at all. Which was still in wide use at the time. How the shit that got through QC, I'll never know. There's no chance, in that year, that someone testing or developing it hadn't tried to load HomeStarRunner or something, or had a Flash ad try to load. Hell I think YouTube might have still used Flash on Linux at the time.

I think the only platforms I've not had comparable levels of breakage with are FreeBSD and Solaris, but then I only ever did one upgrade in both cases, so maybe I just got lucky.

It's great if you've never had problems, I feel envy for you, but some small % of users will have problems due to the sheer number of different hardware and software configurations out there.

Hell, I haven't even managed a single upgrade of OpenWRT without losing a bunch of additional configuration / packages.

There's always at least one driver (or default) that has changed just enough to break something requiring research to fix and usually a couple of packages that have been removed from the repos. So I always figure on an afternoon to deal with any immediate (i.e. booting) issues and a bumpy few days as I have to work out any substitutions.

Just an anecdote to counter your assertion.