After upgrade to 9.1.1 (from 9.1) our TeamCity windows service refuse to start. It took some time to understand it, but it turns out that our 64-bit Java have been replaced with 32-bit Java. This does not make sense to me.
In your help I can see that you are aware of this issue since it states the following: "Note that on upgrade, TeamCity will overwrite the existing JRE with the bundled 32-bit version, so you'll have to update to the 64-bit JRE again after upgrade." I can clarify that not only do you downgrade the bitness of Java, but you also install an older version with known bugs and security risks.
Why are configuration settings changed during an upgrade? Can you please secure that updates preserves the settings we have set up in our environment? And at least give us the option in install dialog to override this stupid behavior. But of course, the best part would be if the default setting was to keep the existing settings.