Although I have upgrade one of my computers to Catalina for the purposes of testing my software, I can confirm that it is a general disaster and I will avoid it on all my other computers. Another example of Apple moving one step forward followed by two steps backward.
I share below a simple terminal command that blocks software update from even suggesting a Catalina upgrade.
sudo softwareupdate --ignore "macOS Catalina"
After executing this command and restarting the computer, when I go to Software Update, it now reports:
Your Mac is up to date --- macOS Mojave 10.14.6
I can now rest easy.