Ok, any help would be great:
After updating to 15.10 and Gnome 3.18, the activities overview has become very unresponsive. Arranging windows from desktop to desktop is slow and when opening and closing the application view, the screen may only update a few frames per second (the more icons, the slower).
I've tried different versions of the proprietary Nvidia driver, tried resetting Gnome settings, updating the icon cache for all themes, fiddling with the vsync settings. Just about everything I can come up with, but nothing makes a difference. When going back to 3.16 the overview seems to work normally, but a reinstall of 3.18 takes things back to a slideshow.
Nothing seems to be taking up cpu time, memory isn't the issue, and hardware should not be a problem (i7 4770, GTX970, 16GB, 120GB ssd for home and root).
The only strange thing I'm spotting, is that the NVIDIA X server settings application reports my GPU's performance level at level 3 (max) almost all the time even without any load, even though it should be set to adaptive mode.