Hi @trobb49,
We put a short list of major features/changes on the Announcements area of the forum for each release, e.g. this one for 3.2.0, and each download package contains a complete set of release notes with a more comprehensive list (e.g. this set of release notes in the 3.2.1 tree).
As you’ll see from the latter list, the changes between releases can be pretty long.
One important thing you’ll gain from going to OJS 3.1.2 or newer is access to the PKP Preservation Network, for which we released a plugin recently.
We generally encourage users to keep up to date, and are putting a lot of effort into rewriting the upgrade scripts so they run quickly and with fewer hiccoughs. This work will be apparent starting with 3.3, but I will add that the upgrade scripts in 3.2.1 are running much more smoothly than with 3.2.0.
Regards,
Alec Smecher
Public Knowledge Project Team