I have just recently upgraded to Kubuntu 9.04 64-bit. It has KDE 4.2.2. in it and it has its ups and downs. One of the great ups is the screen edge actions. By default, the upper-left corner shows a “summary” of all the windows you have open on all desktops. Just move the mouse up there and suddenly you see miniature versions of all your windows.
For crazy people (like me) who have too many windows open, this is a great feature. Just click on a window, and it becomes in-focus / maximized (if not previously).