Installaing KDE 4.2
Add following line to your /etc/apt/sources.list file.
deb http://ppa.launchpad.net/kubuntu-experimental/ubuntu intrepid main
Execute following command to install gpg key.
gpg --keyserver keyserver.ubuntu.com --recv-keys 493B3065 && gpg --export -a 493B3065 | sudo apt-key add -
Now do an apt update
sudo apt-get update
Now you can upgrade your existing kde installation using following command.
sudo apt-get -y dist-upgrade
I started using KDE 4.2 and it's pretty usable. It has polished interface and many GUI glitches are fixed.