I just realized that I should maybe provide a little better idea of who I am and what I do.
My name is Eric Carter--I'm a Development Lead at Microsoft. My team and I are currently working on Visual Studio Tools for Office 2.0.
My team (which fortunately is staffed entirely by people with very big brains that run circles around me) has worked on the VSTO 1.0 runtime and a lot of the guts for VSTO 2.0 including the runtime and programming model design for VSTO 2.0.
While at Microsoft I also worked on VSA and the Visual Studio Macros IDE for several years--my area was the debugger. And I spent a year or so working on VBA for Office XP.
Prior to working at Microsoft I worked on a product called iGrafx FlowCharter for Micrografx (now Corel). There I mainly worked on designing and implementing a brand new object model for that product. ABC FlowCharter (the predecessor to iGrafx FlowCharter) was one of the first products outside of Microsoft to support OLE and have an object model, but over the years the organic growth that typically happens in object models had turned it into a hazardous jungle that just needed to be replanted. Also I integrated VBA into iGrafx FlowCharter while there.
So my areas of interest/expertise are object model design, application programmability, .NET, Office programmability, as well as just general programming stuff and (since I have this lead thing in my title) all the interesting areas you deal with when you're working outside of the code editor (like people and teams and schedules and politics).
I'm reminded of the scene in Anger Management where Jack Nicholson keeps repeating to Adam Sandler “but who are you?” as he tries to tell him who he is in terms of what he does. So maybe I never answered the question in my post title :)