xorg does not detect the heads in the same order than windows on a dual-dvi PCIE X700 This is very user-unfriendly, this means on a dual boot system one of the two OSs won't display any image unless it's tweaked manually to change the primary monitor (hooking something else on the secundary head to see what's you're doing meanwhile. Most users will decide the blank system is broken instaed of hunting and fixing the problem
More info in the xorg boog
That's because the display detection code in X, is not the same code that is used in ATI's proprietary driver in Windows. In order for this to be changed, it will have to be done upstream by X.Org, and my understanding is that it will require a complete rewrite of the ATI display detection code, which is a huge mess, making this particular feature request nontrivial. Feel free to file a feature request in upstream X.Org bugzilla if desired.
Filled upstream as http://freedesktop.org/bugzilla/show_bug.cgi?id=5680