I've not lost enthusiasm for this blogging thing, its just that I've been asked to convert some of my blog entries into MSDN TechNotes and write others afresh to accompany the Visual Studio launch, so I've been busy with notes/articles in work on the following topics among others:

Understanding the SDM Type System
The Four Layer Model of Systems in SDM
Understanding Applications in Application Designer
When and how to use the Default System
The Role of System Designer
Using Systems to Define Services
Designing Substitutable Services
Understanding Creating and Using Toolbox Prototypes
Top-Down Design (published here already)
Why no Class Libraries on the Application Designer (blogged here already)

I will post the finished articles here and/or links to them on MSDN.