Although this month's Catalyst driver set is not out yet, the Catalyst 8.6 BETA driver set has been leaked. Since this is a leaked set, list of changes are unknown. Use at your own risk.
Here is the link to the drivers (courtesy of Guru3D:
Windows XP/XP x64: http://downloads.guru3d.com/ATI-Catalyst-8.6--Windows-XP-Beta-(32|64)-download-1941.html
Windows Vista 32-Bit/Vista 64-Bit: http://downloads.guru3d.com/ATI-Catalyst-8.6--Windows-Vista-Beta-(32|64)-download-1942.html
Installation Instructions:
1.) Uninstall the ATI drivers from "Program Add/Remove"
2.) Install and Run Driver Sweeper with "ATI Display" selected. (It's recommended to do this, so that left over data from old graphics drivers don't conflict with the new ones.)
3.) Restart the computer.
4.) Install the new Catalyst drivers.