That doesn't make sense. Are you saying that Surround gaming will not work under Vista? Eyefinity certainly does, and I can run all three monitors in desktop mode (and using screensavers). Or are you just saying it is easier to make the feature work in Windows 7?
As I understand it ATI's Eyefinity technology is a hardware based solution, and as such the hardware is able to pass to windows what appears as a single monitor at the hardware level, this is how the eyefinity tech is able to work around the WDDM 1.0 limitations, Nvidia's solution however is a software solution at the driver level, something of which WDDM 1.0 does not have the flexability to handle.
With the introduction of WDDM 1.1 in win 7, Nvidia's solution can work due to the addition of "Support multiple drivers in a multi-adapter, multi-monitor setup".
These are the features added in WDDM1.1
"Windows 7 supports major additions to WDDM tentatively known as WDDM 1.1; the details of this new version were unveiled at WinHEC 2008. New features include [5]:
* DXGI 1.1, which features return of 2D GUI hardware acceleration for use by GDI [13] and Direct2D/DirectWrite (but not GDI+)
o BitBlt, StretchBlt, TransparentBlt
o AlphaBlend, ColorFill
o ClearType font support
* Direct3D 11 Device Driver Interface (DDI)
* DXVA-HD DDI [14]
* Hardware video overlay DDI [15]
* Optional AES 128 encryption
* Optional decoding of encrypted video content
*
Support multiple drivers in a multi-adapter, multi-monitor setup" - NOTE: this does not mean SPAN mode form the days of XP.
WDDM 1.1 also changes the way in which gfx and system RAM is used, no longer requireing a duplicate copy of data in the system RAM unlike WDDM1.0 which if you start spanning multiple displays you would find that the system RAM would also get ate up leading to poorer performance.
If there are any WDDM guru's out there that beleive im wrong then please speak up.