Features

Screen Rotation
On Catalyst 8.9 and later ATI drivers now support RandR rotation. After configuring your ati card as usual enter the following string. aticonfig --set-pcs-str="DDX,EnableRandr12,TRUE"

Then restart X11. Your xrandr should work.

Note: Using this command on a Radeon Xpress 200M made Xorg unable to start with some weird error in the amdxmm module. Using this command with FALSE instead of TRUE helped afterward. Note: I also had a problem with that option with a 4850, I couldn't get Xorg to start after setting that option.

Q: Is rotation hardware accelerated? How does performance compare to non-rotated?

Open Source Drivers
ATI Radeon cards 8500,9000,9200 and 9250 working with open source drivers provide OpenGL 3D graphics acceleration.

Proprietary Drivers
Proprietary drivers can be used instead, if so desired, although it is not necessary to use these for the cards listed above.

X server

 * XFree86 and X.org support

Xaa

 * X Acceleration Architecture

Xv

 * One Hardware or OpenGL overlay

TV Out

 * NTSC and PAL support

TV In

 * No support for the built in tuner in "All-in-Wonder" cards.

OpenGL
BUT NOT the OpenGL 2.0 version of the shading language.
 * Provides some OpenGL 2.0 commands

The ATI driver uses a version of the shading language called the ARB extension. The ARB extension was used before OpenGL 2.0 was finished.