When you open a workspace with a newer Desktop version you will have the option to upgrade specific transformers when newer versions are available. This is done one transformer at a time in a very controlled manner where you can review the changes in the current and the new transformer. This is a nice feature, but can be labor intensive for large workspaces. You can choose not to do this, but then you won't take advantage of the better performance the newer transformers often offer.

While upgraded workspaces can be opened with older versions, upgraded transformers will be removed. Make sure you create a backup before you upgrade as Safe suggests.

If you have FME Server you want to be sure the Desktop version is the same as Server, or older. A newer Desktop than Server version will cause issues when run on Server.

New .0 versions are almost always faster. Usually new formats are added, so you want to check that if you are waiting for a new format to be supported. When a new .0 version is available, you can read about the new features and formats in the new features page and the blog. You can also check the detailed changelog, which can be found at the download page, but it is quite a lot to take in and probably better used to look for a specific topic.

All major releases are scheduled, with typically 3 a year - one every four months - we target our major releases around the months of March (x.0), July (x.1) and November (x.2).

This and more about releases can be found in the article FME Release Process and Versioning.

For workspaces that are used repeatedly in a critical production environment, I prefer to make sure that the upgraded workspace returns the same output as the not upgraded one. This can be done using FME, processing an test/develop dataset with both versions and compare the results. This can also be done using FME, the ChangeDetector transformer comes in handy. This usually returns no surprises, but if it does, you want to know about it.

+1 to everything @nielsgerrits​ said. I would like to add that it's possible to run multiple versions of FME on the same computer. If you specify different directories when installing, e.g. C:\\Program Files\\FME2021 and C:\\Program Files\\FME2022 they'll be installed side-by-side. You'll get separate entries in the Start menu as well as in the right-click Windows Explorer menu. On any given moment I have 3-4 different versions installed (my record at one point was 11...)

11 installations 😀 I usually have the one matching my server version, the latest release and a beta build.

In retrospect it was a mistake. When I was betatesting a 3rd party plugin for FME there were some compatability issues and I needed to uninstall all 11 versions and do a clean install to rule those out. That uninstalling took the better part of a day 😅

Thanks for this excellent response. I don't have FME Server or any workspaces that are in critical production environments. I do have a workspace that is exceptionally complex. It creates about 20 csv files (pipe delimiters, not commas). I generated these csv files on FME Desktop 2021.2.3 then on FME Desktop 2022.0 after upgrading. I compared all the files and discovered that every file had at least a few differences. For example, one value changed from "3,1" to "1,3" within a field; both are correct. I suspect that the files are fine, but I wish that there were exactly the same.

One more thing. After I posted this question, I went back to the download page (https://www.safe.com/support/downloads/) and discovered "Additional Resources" at the bottom of the page. It seems like there should be a link to that section at the top of the page. Somehow I missed it.