the goal is "realism". I think anytime a new firmware is released, it stands to reason, you may need plan ahead, and be prepared to review your settings. If Fractal only had 2 customers, I think it is conceivable that one person would have settings that are thin, and the other would have settings that are already balanced.
If a new firmware is released, and improves bass realism or sensitivity, the user whose settings were inherently thin, will report "has full bodied sound now!!!" and the user who's sound was already pretty balanced, will report "sounds muffled/bass heavy/boomy".
There are so many variables and levels of customization within the amp block, that it is impossible to know the impact a firmware upgrade will have, particularly when you factor in the fact, that the modifications/improvements/enhancements affect the factory amps differently, since they take the amp's circuitry into account.
If you upgrade - be prepared to dial in your tones all over again. If you can't afford to commit to that process, don't upgrade. The box sounded awesome when I first got it, and we were on firmware 5 back then.