Now it can be told...I am a developer on Microsoft Expression Interactive Designer aka "Sparkle".  We finally announced the product at PDC last week and I gave a presentation on how we built the product.  I promised the attendees I would blog the content in a fuller way, as there was simply too much material to cram into a 45 minute lunch session...and I will, as soon as I get caught up from a week out of the offiice.

In the meantime, you can learn more about "Sparkle" from this video:

Also, I recommend my colleague Manuel Clement's blog: