I have installed 13.04. I have an ATI card
02:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI RV710/M92 [Mobility Radeon HD 4330/4350/4550]
I had to remove the package xserver-xorg-video-radeon, otherwise the system crashed already at boot. About 2-3 times a day several programs freeze, they do not react to mouse or keyboard events anymore (right now I have for example xsane and firefox frozen). Otherwise the system works, newly started applications work without problems. Any idea what to check?