Everytime you upgrade you should check their webpage before, since they sometimes decide to move folders around or break things... Not really out of the way there. (I've been using it for months before I decided it was not for me. Or was it the other way round?)

If you're a developer, make sure you check out NixOS. The ability to install different versions/builds of libraries and packages side-by-side safely and without containers is a huge win. I typically pin my base system at a stable release, using rolling releases for desktop and dev packages (which is possible even if different versions of libc are needed).

do you really still have to reinstall Ubuntu on upgrades? or are you using reinstall in a more figurative sense?

I use Fedora, and the upgrade process tends to work. I remember there was a time when Ubuntu wasn't so great at upgrades in various situations, but I'd hoped that sort of thing would be fixed by now.