If you are unsatisfied by the Mate Desktop Environment on your Ubuntu 12.04 Precise Pangolin Box, you can easily remove it with following huuuuuge oneliner.
This will remove all the Mate related packages. Just copy paste this in your terminal:
sudo apt-get remove atril atril-common caja caja-common engrampa engrampa-common ffmpegthumbnailer-caja libcaja-extension libmarco libmate libmate-common libmatecanvas libmatecomponent libmatecomponentui libmateconf libmatecorba libmatedesktop libmatekbd libmatekeyring libmatemenu libmatenotify libmatepanelapplet libmatepolkit libmateui libmatevfs libmateweather libmateweather-common marco marco-common mate-applets mate-applets-common mate-backgrounds mate-conf mate-conf-common mate-control-center mate-corba mate-core mate-desktop mate-desktop-common mate-dialogs mate-icon-theme mate-keyring mate-media mate-menus mate-mime-data mate-panel mate-panel-common mate-polkit mate-power-manager mate-power-manager-common mate-screensaver mate-session-manager mate-settings-daemon mate-settings-daemon-common mate-settings-daemon-gstreamer mate-system-monitor mate-terminal mate-terminal-common mate-text-editor mate-themes mate-vfs mate-vfs-common mate-window-manager python-mate
If you have installed the mate extra packages, comming mate-desktop-environment, also do this uninstall:
sudo apt-get remove libmatesensorsappletplugin mate-calc mate-desktop-environment mate-netspeed mate-sensors-applet mate-system-tools mate-utils mozo python-mate-menu system-tools-backends