Minor cosmetic issue, but on my fresh kubuntu installation the mouse click effect leaves artifacts occasionally when clicking, and when I double click the whole effect overlay turns into a black box (which sometimes disappears after the effect ends, sometimes I have to move my mouse over it).

OpenGL 2.0 Native: Sometimes leaves artifact, always creates black box if double clicking
OpenGL 2.0 Raster: Always leaves artifact, can't trigger black box
OpenGL 1.2 Native: Always leaves artifact, double clicking creates WHITE box with text visible
OpenGL 1.2 Raster: Always leaves artifact, can't trigger black box