Hi everyone,
I was personally in quite a lot of pain in order to understand everything there is to WAAD. But working from there, I then typed in a blog post that hopefully might help somebody else understand the 10000' view.
The post is here: http://www.redmond-recap.com/2012/12/03/windows-azure-active-directory-microsofts-stab-at-cloud-identity/
If you read it and find any factual errors or omissions, I would be very delighted to hear about them.
Jouni
PS. My colleague Lauri is also publishing a series of blog posts regarding the actual development implementation. You can find his first post here:http://blog.rytmis.net/2012/12/windows-azure-active-directory.html and the next ones should be available within a few days.