According to ATI, Windows 7 will be the real differentiator between Nvidia and ATI products as the WWDM (Windows Display Driver Model) 1.1 is heavily based on the DirectX 10.1 API. Since Nvidia has yet to introduce any product that is DirectX 10.1 compliant, these features on Nvidia hardware will be forced via emulation of sorts. Some of these effects would in essence fallback to DirectX10 API in order to achieve the visual effects. These effects could also be natively realised on DirectX11 hardware but we would doubt any such product releasing in the next quarter, would be happy to be wrong on this one.

http://gpucafe.com/2009/03/catalyst-...dows-7-driver/