I just finished reading this article over at ars technica. Developers always ask me "why Vista if WPF works just fine on XP SP2?" WPF on Vista is a better experience because of the "plumbing" you will read about in this article.
I think this article does an excellent job explaining the history of how and why versions of Windows prior to Vista render the desktop the way they do. It does a good job of boiling down GDI/GDI+ and User APIs as well as explaining how WinForms is an abstraction on top of them. The article then explains Vista's new Desktop Window Manager (DWM), how Vista uses DirectX, and the relationship to WPF. Once you read it, I think you will have a better understanding and appreciation of the underlying technology which makes Vista look and feel better. The article covers more than WPF, DWM, & DirectX. I think it's worth reading for those of you interested in geeky stuff:).