The main issue most people will encounter with running in test is issues with the new code and extensions designed for previous versions not working as expected and/or raising errors. You'll probably experience a lot more of the latter the more extensions you run. If you're not running community extensions then you probably won't experience too many issue if everyone is running in test.
Note - whereas if the GM updates to test, but the players don't, the GM will share only the new test ruleset changes with the players when they connect. They won't share any changes in the underlying application, the players will also need to switch to test and do an update.
Generally, if the release notes don't include a ruleset name against a specific item, the change is in the base FG application. Info on test release v3.3.7 here: https://www.fantasygrounds.com/forum...l=1#post414081 It can be seen that the main memory improvement change in test is not tagged for a ruleset, so is in the base client: "Player image loading delayed until image window opened." So players will need to change to test as well to experience this new functionality.

