KDE 4.4 was released on the 2nd of March 2010:
I am currently running Kubuntu 9.10 which by defualt has KDE 4.3.2 but the KDE 4.4 packages are available for the adventurous. So, why would you want to upgrade? Well, 4.4 is a bigger number than 4.3 right so it is therefore better 🙂 KDE 4.4 is based on QT 4.6 versus KDE 4.3 QT 4.5 so that comes with its own benefits. Also, if you do any KDE development you will need to have the latest and greatest KDE to develop off the trunk.
So if you can’t wait for the packages to reach the main repositories, here is how to do it, it is quite simple:
sudo add-apt-repository ppa:kubuntu-ppa/beta
sudo apt-get update
sudo apt-get dist-upgrade
Remember though, it’s beta, so if anything goes wrong you could be stuck. Roll back is not something that aptitude does very well at all.