For example, in moving from Maverick to Natty, Banshee replaces Rhythmbox as the media player. But if I had installed a player different from either one of these, and uninstalled Rhythmbox, how would the distribution upgrade behave? Would it still install Banshee? What if I simply uninstall and then reinstall Rhythmbox? Will it upgrade to Banshee?
Months ago, on the Lucid to Maverick update, I got impatient and made the upgrade a week or two before the final release. At that time, the new Ubuntu font was not implemented, so I downloaded and installed it by myself. When I upgraded to the final version, of course I had the font, but it was not set up as it should have been, with the correct font sizes. I fixed them manually later. I suppose that this happened because the system "considered" this to be a personal setting which should not be changed.
My main question is: How does the system "know" whether I want to use a particular setting as the default, thus upgrading it according to the new version, or if that setting was actively set by me and, in that case keeping it intact?