My Catalina upgrade was a headache. Here is a bullet list of my woes:

• The install process stalled for about an hour on “Setting up your Mac”. I eventually gave up waiting and forced my Mac to shut down. Luckily, after a reboot, the installation continued and completed in mere seconds.
• System Preferences alerted me that there was a problem with my iCloud account sign-in. Entering my credentials again (several times) did not resolve the warning. I ignored it, at first, until I discovered the following two items.
• All my iCloud drive files in the Documents and Desktop folders were missing.
• My iTunes library was not displayed in the new Music app. I eventually found a preference that had to be enabled that brought them back, after a slight delay.
• To fix the iCloud account and iCloud Drive problems, I signed out of iCloud Drive. During the sign-out process, I let it back up all my files to a local folder, which took a long time. After the backup finished, I signed back into iCloud, and iCloud Drive re-downloaded all my files. It took a while for my files to re-appear; the wait was stressful, even though I have backups.

This was another one of those years in which a macOS upgrade made me wish I was an iOS (and now iPadOS) user only. That said, my computer did not get bricked, which happened with an automated Windows 10 update on one of my other machines a little while ago.