I also try to rotate my screen to no avail. I have an AMD 690G motherboard with integrated Radeon X1250 graphics and I am using Debian sid with the latest ATi driver (8.39.4). I can only change my resoltion with xrandr -s, but no rotation or reflection. I tried the VESA driver too but it won't let me rotate the screen either. Could it be that there is simply no support for rotation in the driver from ATi?