Seems that Microsoft, with the future Longhorn versions, plans to offer three different graphical interfaces, each requiring a different level of graphics card.
The top interface (named "Aero Glass") will have transparency and other advanced 3D shading features but will demand a high-end video card with at least 64MB of video memory. The midlevel interface (named "Aero") will offer most of the improved graphics abilities and will require just 32MB of video memory.The low-powered interface will have an interface designed to replicate Windows 2000.
I think this is a great choice... 
Users could choose the graphics environment that they want easily. I hope that this requirements (64Mb for the best interface) could be respected, but I think that they could be not enough 