GPU usage is right up there at the top. Temps are fine. I am on latest stable drivers, but I did try 12.8 as well. I flashed to the GHZ BIOS, but am back on original. I am now up to 590 khash, and my clocks are 965/1575. At these clocks I would expect much more at -I 20. This card still isn't as fast as the 7950. I really think there is just something about this card.
FYI to get close to or over 700 kh/s, you are going to be looking at RAM clocks in the 1700 to 1800 + territory.
Keep an eye on temps. Sometimes a slight overvolt to the memory can help with stability. I'm running 7970s with Arctic Accelero coolers for this very reason.