I noticed that I can't avoid losing all my MATE settings during upgrade from UP6 to UP7. I did the upgrade on a 32bit system and the MATE theme settings were all reset to default, all the panels became Debian default. Even mate-terminal profile was reset to Debian default. Mate-power-manager even defaulted to the default settings.
What gives? I never had this happen when upgrading UP4, UP5, UP6, etc. Very annoying have to reset everything!!!
I thought it was just perhaps a bad upgrade, but I later upgraded a 64bit system on UP6 to UP7, and viola. Exact same thing happened. It was like booting into a brand new Debian system, as opposed to my existing LMDE setup.
I made sure I selected NO for any "do you wish to overwrite your existing configuration file with the new one?"