Originally Posted by clarious
I also has the same VGA card like you (8600M GT), same nvidia driver version (185.18.04), xorc-server 1.6.1, QT 4.5.1 and KDE 4.2.2 but I have no problem with Kwin/OpenGL mode at all. Hovering mouse over those buttons only make X consume 2~4% CPU
In this case I will try a kwin revision from around the 4.2(.2) (or the one from 4.2.2 if it compiles) release and see if this helps.
btw. regarding PowerMizer: Indeed for normal desktop usage most of the time it stays at the lowest level (0). But even in most cases the expose-effect works smoothly at the lowest level, so changing button images should not be too hard?