The newest versions do have some improvements that may be worthwhile around reusing TCP connections to the indoor units and avoiding double-polling. Both changes will take it easier on the indoor units' hamster-driven TCP stacks and so may be more reliable. There's nothing software can do about poor WiFi signal, of course.
Your existing kumo_cache should be fine. I would recommend keeping a backup copy in case of issues.
Of course, if anything breaks, you get to keep all the pieces.
Just in case this is useful to anyone else, I have updated, all is well, and I still have local control of the heat pumps using my prior kumo_cache. No comfort v3 app for me! Hopefully this will make the "hamster-driven" mitsubishi adapters happier (or at least decrease the log spam).
I just installed the Kumo integration app and the login screen will not take my comfort app login and password. I tried changing my password to verify I'm typing it into the intregration login correctly and still getting an Invalid credentials error. Any ideas on what i need to try? Thanks
Mitsubishi broke this. Their cloud APIs in the US no longer supply the credentials necessary for local control. I myself (hass-kumo/pykumo author) recently added new heads and had to go the esp32/cn105 route. If you have a working setup, do not reconfigure things and do not lose your kumo_cache.json file.