At our insistence you came back with valuable examples :) Please come up with more.
I see your point with the shortcuts, the SystemSettings application does not show all global keyboard shortcuts, only the ones of KDE4 applications (I know my old Amarok has reserved some, but they don't show up there). So yes, I don't know any way of finding a global shortcut; was there one in KDE3?
I don't know about buggy taskbar and screensaver, but please report bugs. For the global shortcuts I'll put a bug myself (but unfortunately I wouldn't know how to also make the fix).