In relation with the recently reported bug #1378 
http://bugs.pearsoncomputing.net/show_bug.cgi?id=1378
got my attention thing prepared for KDE4:

http://www.h-online.com/open/news/item/KDE-display-management-to-get-a-boost-with-kscreen-1774693.html


Often I see spreading window sizes when turn on / off secondary screen or 
switching from internal laptop screen to external and back. Another problem 
is that after restoring a maximized window may be restored onto already 
unavailable screen. When turn on the second screen will also become invisible 
in the taskbar windows that were open in single-screen mode.

Note: I know, I need to add information about these issues to bug message.

Slavek