Catalina intentionally changes some core functionality going forwards, mostly for security reasons, and breaks a lot of old software, including *all* 32-bit software, which will *will no longer run* - this includes apps, utilities, drivers for hardware, 64-bit apps that link to 32-bit libraries and so on...
If you are interested in how this will affect you, there is a good utility called "Go64" available free here:
https://www.stclairsoft.com/Go64/index.html
If you run this in your system, it will scan your software and show you will apps that *will not run* on Catalina, so you can get an idea of what software you'd need to upgrade, replace or find alternative solutions for, should you want to upgrade.
(On my machine, there were over 1000 apps that were either 32-bit, or mixed 64/32-bit code, that won't run on Catalina.)
You'd also need to check the drivers for all the hardware you are using - if you are using scanners, printers, audio and MIDI hardware with drivers etc - you'll need 64-bit drivers for all of them, otherwise *they won't work*. In some cases for older hardware, that may mean new hardware purchases.
Also, due to the new security model, there are additional impacts where on first use under Catalina, more or less every software you use will request permissions to do things that they've been happily doing on your system for years, like accessing the file system and so on. This will be initially quite annoying, and you'll need to factor that hidden cost in.
There are also the usual bugs and issues with a new OS release. One impact is that as iTunes has been deprecated in favour of the new "Music" app, it's broken iTunes integration with apps that can look inside iTunes libraries - so things like DJ apps that can use your iTunes libraries for source material have problems.
My personal advice is, that if you are a light user, with a more or less default system, and your main use is web/email/social media and maybe a main app or two like Logic to make your art, and using little or no older hardware, you'll probably be ok.
For 99% of the rest of us, it makes little sense to upgrade at this time.
If you *do* want to try, I recommend you clone your system disk to a separate drive, and install the new OS on this drive - this will let you test the impact of the new version for yourself, without irretrievably damaging your current systems, and will let you easily revert should you need to. Once you're happy with the new system, then you can commit to it at a later date.
In summary - Catalina is a bit of a pain point at this time on the sort of systems most of us are using, and there aren't that many (imo) compelling reasons to upgrade. Give it a good 6 months or more for things to settle down, and for you to assess the impact of upgrading on your system, before thinking about it.
For the small few who like a gung-ho bleeding-edge approach and just want to go for it and see what happens - good luck, and let us know how it went!