I gave a talk at PDC 2003 back in October, and haven't managed to mention it here since then.  Here's the abstract:

Avalon Graphics and Media (Part 2): Using Graphics, Animation and Composition in Your Applications
All Windows "Longhorn" application developers that make use of graphics to create exciting applications and controls will benefit from this session's essential knowledge, including the extensive set of graphics primitives and capabilities. For those developing specialized graphics applications, the advanced rendering concepts and capabilities provided in Longhorn will be covered, such as composition, the key graphics abstraction Visual (used for off-screen rendering and printing), and the imaging pipeline.

It was a great experience, and the session dove into a bunch more detail and structure of the entire Avalon system than had been discussed previously.  If you're interested, the slides can be found here.  There's also some sample code that I discussed and walked through during the talk, and it can be found here (it runs on the PDC version of Longhorn).

All sorts of information from the PDC can be found here.