I have no problem on my desktop.
However I did have many on another one with gentoo .... mainly because of dev-qt/qtcore-4.8.4-r2.
I may be lucky on sabayon OR sabayon integration team did a good job.
Actually I just have a problem but I dont remember if it is linked to KDE upgrade.
From time to time usually when I click on a link on FF session is existed and go back to login screen.
I cant reproduce it now