There's a fairly good article on some of the key points of Office 2007's programmability experience at http://www.adtmag.com/article.aspx?id=18978

I don't directly work on this at Microsoft, but have been following it more as a user.  I am really interested in the notion of a "business data catalog".  The interviewee talks a little bit about this specifically:

The major advance there is the business data catalog. This is a facility that developers would use to define Web services that access back office data  so if they have ASP in house, for example, they can use the business data catalog to define a Web service that provides access to inventory or ordering, or whatever functions that they have—the ASP backend. What is important about this is that the business data catalog will have common definitions. So the way I think it is going to go is there will be typically one or two developers who understand the backend data really well. They will define Web services interfaces to those systems because they understand those systems. Then other developers can use the Web services that are defined within their applications so they don't have to learn the intricacies of backend systems, which can be pretty complex, to access the data in them. So you are basically creating a reusable integration point that lots of developers can use.

Going to have to play around with that!

A really appealing idea to me is to combine this protocol-normalized data bank with the existing Office APIs and a very light weight scripting IDE that lets you snap together tiny applications.