Long Zheng posted an interesting screenshot taken from the presentation by Anantha Kancherla which was about
Writing Your Application to Shine on Modern Graphics Hardware. It contained a sheet that mentioned that Windows 7 will cut memory usage in the graphics system of the Windows 7 Desktop Windows Manager by 50%. The same chart mentioned that the Windows 7 desktop manager will make use of the Direct3D 10.1 API which probably meant that it is supported if the video card is supporting DirectX 10.1. It is unlikely that Windows 7 will require a DirectX 10 video card to run at all given the current market share of those video cards.
It is nevertheless refreshing to see that Microsoft is optimizing not only the functionality but also the resource usage of the operating system.