DirectX technology in Windows Vista® has undergone an enormous amount of change while still maintaining backward compatibility with previous versions. The DirectX Developer articles provided in this space discuss various aspects of developing with DirectX on the Windows Vista platform.
A User Perspective for DirectX discusses the improvements in to DirectX in Windows Vista that will be experienced by gamers and other users of the technology.
A Roadmap for DirectX summarizes some of the new Direct3D features from a development perspective and points to documentation that covers each feature more thoroughly.
DirectX Development contains a number of articles focused on specific Vista development issues.