Differences between Excel 2003 and 2007 from a VSTO perspective

Question

What are some of the major differences to be aware of when developing Addins or Document level customizations for excel 2003/2007?

Answer 1

A couple items:

VSTO 2SE - can be used for both Excel 2003 and Excel 2007 addins. (requires code-access security on installation)

VSTO 3 - can only be used for Excel 2007 add-ins. (Does not require code-access security)

Excel 2003 - can install add-in for all users or per-user.

Excel 2007 - Can only install add-in per/user.

Answer 2

http://weblogs.asp.net/spano/archive/2007/06/10/working-around-vsto-se-s-lack-of-document-customization-for-excel-2007.aspx

I found this article which outlines the issues clearly.