What's the problem, is it stuttering?
place my config in your BF3 folder
http://www.qfpost.com/file/d?g=SooKYHpUA
BACKUP THE OLD ONE FIRST, if you have it
Plays fine on my rig in sig, never had any problems running the game with SLI.
At work so cant watch video, what driver are you running? Have you got the Crossfire profiles installed off ATI website?
Do you get the same problem when you run a single card?
Have you got MSI Afterburner installed to monitor gfx card usage, temps, etc.

What resolution are you playing at?
What are your in-game settings, High, Ultra etc? Do you change these when you go from single gpu to crossfire?
i think you will always find the people that hate it, people that like it. It just works for me so its all good in my eyes. have worse luck getting true eyefinity support (how hard can it be to keep a HUD centred)
However, on the point above I'm not sure how long you would have to wait to get a single card more powerful than two 680 or 7970's? but at a guess i would think a fair amount of people buy a second card once they go cheap. gives them extra bang without loads of buck.