This page on MSDN provide a very cool matrix of which features are available for development depnding on your mix of VSTO version and Office version.
http://msdn2.microsoft.com/en-us/library/aa942839(VS.80).aspx
About Shiraz Cupala
Shiraz worked for 10 years at Microsoft in product design, web development, customer research, and online marketing roles. Over the first 3 versions of Microsoft InfoPath he managed Outlook, Excel and SharePoint integration, the hosted InfoPath control, IW and developer programmability features, product usability, and internal solutions. He has architected numerous small and enterprise level InfoPath solutions including for collaboration, publshing, and finance, including the InfoPath solution for Microsoft's expense reporting system. Shiraz holds a Bachelor of Arts in Philosophy from Tufts University.