Just anecdotally : I have my grandmother, brother, and his mother on Kubuntu, and my mother on Lubuntu. So far, the most updates anyone has gone through is 3 (my mother went from 10.04 to 12.04 to 14.04 and soon 16.04) and we have never had an issue. Oh, and you get to chose when to do the upgrades rather than having them backdoored on you.

Desktop Linux works fine for regular people. They aren't going to go digging in the terminal to brick their own computer. Show them the software center and that their app store uses things online called apt links and anyone with a smartphone understands it fine.