nvidia, but desktop effects are disabled (I saw some reports related to this)
When attempting to adjust volume, pressing volume up/down buttons is often extremely slow to respond. Often plasma will appear on screen and remain permanently.
Right click on kmix plasma often takes extremely long to respond.
I don't think this was true on kde 4.10.1 (but you never know, could be due to some other 'upgrade')
It generally gets slower due to (apparently oxygen-related) kmix memory leak, bug #309464
*** This bug has been marked as a duplicate of bug 309464 ***