One of the great things I like about Ubuntu (and other linux distros) which astounded me after using windows is the benefits of storing the user's settings in their home folder.

I have always kept my /home partition separate from the root partition (which I think the Ubuntu partition setup should do as default) so when you re-install ubuntu, all your settings are restored, color-scheme, wallpaper, etc.

After installation, as you re-install the applications you used to have each app picks up it's previous settings with no hassle.

However, although all the settings are still stored, you still have to go through all the applications you had installed previously and re-install them from the package manager.

"My Ubuntu", would be a little application that you run and it would present you with a list of the applications you have installed at the present time. This would not be at the lib or version level, but be at the application name e.g. Gimp, Cheese, i.e. the identifier that would be put in the main menu.

From this list you can de-select any apps you are not interested in and then click a save button, which writes the list to a file in your home folder.

After doing a re-install you then simply have to install "My Ubuntu" (it would be nice if it was installed as default eventually), select the previously saved apps list file and it will then go through and ensure all the apps on the list are installed.