It's been quite a while since we had a kernel architecture video. The last one (pre-Vista, I believe) was pure awesome. There have been some since that talk about specific optimizations, but seeing the overall work and talking about cleaning up the dependencies and modernizing the older stuff would be cool. Or, whatever they are allowed to talk about.
WP7 stuff is a must. The specific programming topics are cool, but there are a lot of things that we'd like to know about. How will the OTA updates work? How often will the OS and API's be updated? How often will the hardware be updated?
I think we'd all like to meet the new members of the C9 team.