I'm having a strange issue occasionally where my cursor will disappear while not in motion. When I move the mouse it will reappear, along with a small chunk of the screen as it was before it vanished (that part doesn't hang around for long though).
This issue is random but will exhibit itself immediately upon logging into Plasma if I have OpenGL 3.1 (or 2.0) as the Rendering Backend. The only way I've managed to fix it is by rebooting several times in hopes that it fixes itself, or using XRender for my Rendering backend (which sadly disables awesome blur effects).
I'm using Scale method: Accurate
Tearing prevention ("vysnc"): Automatic
Keep window thumbnails: Only for Shown Windows
Allow applications to block compositing is enabled.