This is pretty cool, but I still doubt the usefulness of this. Power consumption aspects aside, if your GPU is powerful enough for accelerating HD playback, it's likely your CPU will be powerful enough to do it alone. Also keep in mind that with Gallium's partial acceleration, a fair bit of CPU power is still needed, especially with H.264.
No announcement yet.
Gallium3D VDPAU On Radeon Starts Working