Version: unspecified (using KDE 4.4.2)
My laptop has two keys (Fn+F7 and Fn+F8) to change screen brightness. The global shortcuts in KDED automatically got correctly assigned, and when I hit one of the keys, I get a bar on the screen (similar to the one to change my speaker volume) showing the current brightness. However, it does not actually change brightness, just displays the current value. I can perfectly well change it using the power management plasmoid, and the changed value is reflected in the KDED on-screen display triggered by the keys.
I am adding this to "unknown" since I have no clue which part of KDE is responsible for this.
This is still an issue as of KDE 4.5.1.
*** This bug has been marked as a duplicate of bug 181444 ***