Just wanted to chip in that I've installed these for my crossfire set up and it's been a breeze. On 12.8 the zero core feature for crossfire (for me) was patchy. With 12.9 beta's the zero core works flawlessly (literally i alt-tab to desktop from game and the 2nd gpu drops immediately).
I'm getting 98% gpu usage on BF3 from both cores and silly fps. Played 2 1/2 hours last night and not a single hint of an issue. Also work well on GW2 (though usage is lower, which isn't a problem as it's well into triple figure fps, so i wouldn't want full usage).