KDE 4.4.3 has been out for a bit and finally came to Debian Squeeze recently. You may have been running it sooner on Sid. The first thing I noticed was that when I logged in all I got was a black screen. No wallpaper, no clicking the desktop, and I couldn’t see any task bars, etc.
This was annoying.
I googled for a long time and never found an answer, but fret not my fellow Google warriors — the solution is here. Simply install plasma-desktop and you will be good to go.
aptitude install plasma-desktop
Don’t ask me why this wasn’t pulled in by kde-standard.