KDE4 is the newest version of the K Desktop Environment.
You can read more about KDE4 here.
On this version, KDE had achieved its goal.
KDE has been looking for ways it can improve the desktop interface, offering the prettiest desktop on linux. And on KDE4, it had achived it’s goal!
KDE4 offers a Mac style interface with Windows navigational system, attempting to make new commers become more familiar with the style and look.
Although, there is one down side of this eye candy looking desktop environment. KDE isn’t designed for performance so it is very much memory consuming. Both KDE3 and KDE4 continuously freeze both my virtual machine and the actual computer. And the startup process is slightly slower than Ubuntu (GNOME).
And here, I reveal the latest KDE4 on Kubuntu 8.04 since it has more seders than the Kubuntu 8.10 upcoming BETA.
KDE4 Startup Screen: