Just a note. I didn't flash mine, but radeon tweaker works wonders. I love having the profiles you can just load.
many people over at Rage3d are reporting that the bios flash does NOT enable hyperz just sets the default clock to 166. So most are running radeon tweaker anyway. Some have reported their scores over the past weeks and the differences in performace between flashed and those using radeon tweaker were negligable.
Flashing carries with it certain risks, radeon tweaker involves less risk.
By the way I had little success with raid-on tweaker by Humus. But really like radeon tweaker.