I'm going to have to wait to complete my AVALONfiltered series of articles. According to some stuff I've heard and read from Microsoft, the June 30th Beta release of Longhorn and Avalon will have some rather significant changes since the March CTP. I've personally been trying to get Microsoft to add MERGE MODES / BLEND MODES. I hope they add that in Beta 1 or Beta 2 - or at least when they finally release Longhorn. Nate Dunlap (Designer, Avalon Team) has told me that he also wants merge modes put in the Avalon core, and Pablo Fernicola (Group Program Manager, Avalon Team) has also expressed interest in it. It's really cool that even such big wigs at Microsoft listen to the little people. 
So, I'm holding off on writing the articles (although I have written at least 6 pages now) until June. Beta 1 will bring important changes and I really dont want to rewrite anything - nor do I want to be proven wrong if Microsoft decides to take something out!! I vehemently hope they don't pull anything out.
I'm still open to feedback and suggestions for the AVALONfiltered articles.
Update:
I forgot to mention, Microsoft has pulled out Longhorn 4074 (WinHEC 2004 Build) from the MSDN Subscriptions. This means that they might put up Build 5048 from the recent WinHEC (2005). Let's see what info I can get from the people at Microsoft.