First I'd like to say I discovered this by accident and have no idea why it works. I alt-tabbed out of the game to search for a quest on the web, then when I alt-tabbed back to the game (took two tries, the first try only gets back to a black window), the game was running significantly smoother. I've been doing this every time I play since, and every time before alt-tabbing I'd experience stuttering, however after alt-tabbing it's much smoother. It works for both eyefinity and one screen. My configuration is 6970+6950, 11.10 preview 3, cap 4. Once again I have no idea why it works like that, and this might not work for you, but it's worth a try.