This includes support for all newer Radeons, including the 2900 series. Among the improvements for this set include performance enhancements for some games, with figures of 16% listed for HDR supporting games. They fixed issues with certain resolutions not being available on Vista with CRT monitors and posted a laundry list of various other bug fixes, which you can see in the release notes on the driver download page.
On the Linux side, AMD has released the 8.38.6 driver package, which brings support for RHEL5 and works fully with Xorg 7.2. However, there are still issues with the Composite extension, as there has been for some time.