I’ve already upgraded to Catalina and it works fine for me
There is a very small group of people who ran into a small problem when upgrading to Catalina, this is a much smaller group than usual so this is excellent performance for a major upgrade
There were a small number of software developers that never bothered to check their apps for 64 bit compatibility and so they are not working correctly now. They had an entire year to check (it literally only takes a minute or so to check it, so there is no excuse for not checking it). This is basically a handful of extensions on Adobe products (Adobe has no excuse, they make billions per year and they have hundreds of software engineers)
The makers of certain DJ apps did not check to see if the new Music app that replaces iTunes would output XML files which the DJ software uses to play the playlist, it turns out that Music.app does not output XML and Apple told them that but a few of those developers did nothing to prepare for Catalina.
Other than those two tiny groups, everyone else is doing fine
Catalina has a new feature where you can restore Mojave (using Recovery mode) if you run into an issue with Catalina but you only have 24 hours to decide and then the old OS is deleted so that you can regain your disk space.