By upgrading the drivers to a leaked beta version of what might be AMD’s next official drivers, others and myself have managed to successfully render with OpenCL acceleration, however that is in Blender 2.6.2 official release.
In Blender 2.6.3, it renders only few shaders and the rendering time is bit longer.
But here are the steps you need to take in order to get it work and test it yourself.
Get the leaked drivers here: http://www.ngohq.com/home.php?page=Files&go=giveme&dwn_id=1624
Choose and get the official Blender 2.62 according to your own OS here : http://download.blender.org/release/Blender2.62/
Install them, and search for the file kernel_types.h which should be in the folder C:/…/Blender Foundation/2.62/bin/scripts/addons/cycles/kernel/
Open that file and uncomment that piece of code :
Save it and you’re done. Launch Blender and try !
By the way, Linux users may need to wait till the end of the month when catalyst 12.5 will be officially released.