On 11 December KUbuntu announce KDE4 RC2 releas

The second release candidate of KDE 4 has been released and packages are available for Kubuntu 7.10.

If you want to test KDE 4 without installing packages download the live CD (466MB). This CD includes a preview of the Konqueror Webkit engine.

They install to /usr/lib/kde4 and can be installed alongside your existing KDE 3.