Those of us who are using KDE 4 packages from Debian experimental may want to stay up to date with the last packages available. It happens that, by defect, apt[itude] will not upgrade them even in a [dist-upgrade full-upgrade]. So, what to do in this case?
Put these lines in /etc/apt/preferences (create the file if it doesn't exists):
Pin: release o=Debian,a=experimental
That's all, now upgrade your machine :-)
Many thanks yo Modestas "MoDaX" Vainius for the tip :-D
Update (09/07/2008): this will only upgrade those packages that you manually installed from experimental, but not all the packages from experimental.