After every major update having to remove "zeitgeist" if it has been re-installed is my biggest complaint. Furthermore, Nautilus (the default file GUI) depends upon a zeitgeist library, so unless one is very careful to remove zeitgeist but leave the library, Nautilus (the default file system GUI) is unusable. (Eventually I stopped using Nautilus because of it).
Zeitgeist remembers all your activity and stores it in a database and some people find this very helpful - no problem with that but opt out once should mean forever. It was a huge CPU drain and wearing out the SSD. Also, it has/had a GUI feature that allow removal of sensitive info -- I tested that and check the digital zeitgeist database blob to see if the into was really gone -- actually it was still in the blob (visible in the raw data as ascii) but no longer visible from the GUI, a state that contrarily highlights the sensitive bits. I'm not a conspiracy believer, it's just just the principle.
But I'm still using Ubuntu due to momentum - and also because of reasonable package maintenance, that clumsy snap notwithstanding. Also, LXC works great in Ubuntu, not surprising as Canonical is the developer of LXC.