UPDATE TO CATALINA - MacBook Pro

The one major issues I have seen for some users is those who have a lot of old software, including some printer and other peripheral drivers, that is still 32 bit. See:

32-bit app compatibility with macOS High Sierra 10.13.4 and later - Fairly complete FAQ - https://support.apple.com/HT208436

Catalina did away with 32 bit support so people who have software such as Microsoft Office 2011 are finding they now have to subscribe to Office 365 or find alternative Office package. Apple has its own free Pages, etc., and there's free LibreOffice and OpenOffice.

The other thing I have seen are reports from people who have older printers or projectors. Some companies have simply ignored long-time advance notice this has been coming and those users are left with devices that are not seeing updated drivers.

Then there's other legacy software such as something highly specialized where the developer simply stopped upgrading or is maybe no longer alive. The only thing to do there is to either not upgrade at all (but eventually you will have to since new Macs will require Catalina or newer), or to have a separate boot system for running those. Or maybe a variant on that and run an older operating sytem version in a virtual environment using something like Parallels.

You should review your position. Maybe you don't need Catalina yet. I never see any harm in letting the early adapters rush in and do the bug testing, then wait a month or two and then install something. ;-)

It's been my experience that the people who avoid disasters and complications when upgrading their computer's operating system share a few things in common:

1. they back up their computer before starting the upgrade
2. they check to make sure their software is compatible with the new OS
   1. most especially the software they cannot do without
3. they check to make sure their peripherals (printers, scanners, etc) are compatible with the new OS
4. they check out a few articles to see what changes have been made in the new version - is Apple (or Microsoft) taking anything away or drastically changing something they find important?
5. they wait a couple days/weeks/months and let others find all the problems.
6. they back up their computer before starting the upgrade (yeah, I deliberately repeated myself)

Most of the time the people who do all these things don't need that backup because they knew what to expect. But its better to be safe than sorry.

I ignore rule #5, I've always lived on the bleeding edge - I'm a nerd and always have been. But my best advice besides those 6 rules above are wait. There's no need to hurry. There's nothing so exciting about any upgrade that it can't wait a couple weeks.

And if you just have to be a nerd, then follow rule #7 -Using cloning software like CarbonCopyCloner to copy your computer's hard drive to an external drive. Then apply the upgrade to that external. You can test drive the new OS and your software and see if you like if. If not, erase the external and go back to the tried and true. If you do like it, install it on the internal drive - after following rule 6