And finally to upgrade to KDE 4.3:

#sudo aptitude update && sudo aptitude dist-upgrade

Or, if you don’t have KDE installed already:

#sudo aptitude install kubuntu-desktop

It is better to use ‘aptitude’ because if you don’t like your new desktop you can simply uninstall the packages with all its dependencies and you are back to the system state where you were before. That is not possible directly with apt-get (or synaptic etc.) (works with –purge but I find aptitude better, but let’s not get into a pointless discussion). But if you normally use apt-get, than use that instead of aptitude!

Removing KDE 4.3 from Jaunty

Removing KDE 4.3 from Jaunty and going back to 9.04 KDE version (4.2.2)
To revert back to the default KDE version in Kubuntu 9.04, you must firstly remove KDE entirely:
If you installed it using aptitude, not apt-get:

#sudo aptitude remove kubuntu-desktop

If you installed it using apt-get:

#sudo apt-get autoremove kde –purge

or

#sudo apt-get autoremove kubuntu-desktop -–purge

Then remove the newly added repositories press Alt + F2 on your keyboard and enter:

#gksu gedit /etc/apt/sources.list

and in this file, search for the 2 added repositories (from the beginning of this post) and remove them (they probably are at the bottom of the file). Then open a terminal and:

#sudo aptitude update && sudo aptitude install kubuntu-desktop