For the most part, the initial upgrade to macOS Catalina was uneventful; I was caught unaware by the wave of permission requests that greeted me but it was 2 minutes of clicking accept or deny and continuing on with my day (though, how normal users will cope is beyond me... it feels very un-apple).
The two issues I did run into, were the need to reconfigure Google Drive (again, a minor 2-minute activity) and trying to get VSCode to work properly. This was a lot more annoying. The initial issue was that git, could not be found... this broke all of source control in VSCode. The fix was to run the following from the terminal:
xcode-select --install and restarting VSCode.
Once that was fixed, the next issue was that I could no longer sign commits with GPG, this gave a similar issue as the initial Git not being found.
The correct fix for VSCode is to add it to the list of Developer Tools which you can find under Security & Privacy. Once a restart of VSCode everything just worked. I added Terminal to the list too which also stopped autocomplete from Fish Shell from constantly prompting too.