This power management implementation permits the r600/r700 GPUs not to burst into flames.
It will be, when the new radeon power management code (which implements voltage variation, too) currently in the "drm-radeon-testing" git branch will be merged in Linus' development tree for 2.6.35. A week or two. Or three.
The developers implemented a sysfs interface which permits enabling a dynamic power management, or a single power state for the GPU/memory.
And that's great.
But I haven't tested it all, yet. I'll report if I do, before the mainline merge.