It is always the little things that add up. For example, I had added a mail account for Gmail, but had disabled it. Mavericks enabled the Gmail account. No big deal, but annoying.

All in all though, this was much easier a way less annoying than upgrading a PC to a newer Windows version! And more things still worked in Mavericks than I usually experienced with a Windows upgrade. Of course my Mac Mini is barely a year old and all the software apps are fairly new as well, so less likely to have issues than I would on an old Mac.