Well, with a running Debian Sid distribution, I am all set to test KDE 4. The installation process is simple enough but, before getting into it, remove any previous version of KDE. Here is how I’ve done it :
deb http://ftp.fr.debian.org/debian/ experimental main contrib non-free
deb-src http://ftp.fr.debian.org/debian/ experimental main contrib non-free
aptitude -t experimental install kde4
Note that I first tried to install kde4 using apt-get and it would never work, I had dependencies error, but it worked right away using aptitude.
On the snapshot above you can see three of the built in widgets for KDE, the clock, the post its and the twitter one 😉 Handy. The widget engine is supposed to soon handle the MAC OS X ones. Congratulations to the KDE team!