"Well, everything worked fine until you installed that [Chrome | Firefox | Opera] thing on my computer." Doing free tech support for non-technical people is a wonderful thought, but it can also provide a harsh lesson in the dangers of unlimited liability for open-ended, no-fee, no-contract work.
Anyway, I installed Linux on my mother's system over Win XP years back and it couldn't have gone better. She has been doing great with Ubuntu for 2 years now. The spyware, failed updates and odd networking failures I was summoned to her house to fix frequently went away entirely, so thankfully it was the opposite of your warning. I guess the lesson there is to only provide the best technology, that you trust. Linux is pretty rock solid for home users today, especially people like my mother who primarily use a browser.