VBA to VSTO: Resources
There really isn't a lot of advice out there on how to approach migrating to VSTO. I came to VSTO from the perspective of a long time Office VBA developer. For me, the things I spent the most time on were developing an understanding of .NET/COM interoperability and the draconian VSTO security and deployment model. If you're coming from VSTO with a lot of .NET knowledge, but not much Office knowledge, you're going to spend a lot of time learning the Office object models. Oh, and the draconian VSTO security and deployment model. If you fall into the latter camp, my advice may be of limited value.
Microsoft historically has positioned VSTO as a tool for "professional developers". Something about that always seemed a little off putting to me, but that's another story. Perhaps one of the reasons they went this route was that you really need to have some additional understanding in order to move to VSTO and .NET. Take a look at this post from Andrew and you'll see what I mean. OK, Andrew may be a bit pedantic. Still, when you switch over to VSTO, you really need to be cognizant of the issues involved with .NET/COM interactions.
Should that scare you off? Not in the slightest. As I read Andrew's post, I was reminded of all the minute details I learned back in the days of WOSA along with the intricacies of how COM and OLE worked. I didn't necessarily need to know this stuff as an Office developer, but it definitely made me a better one. Learning .NET and VSTO will make you better too and it's no harder than the things you had to learn in the past.
OK, enough of the rambling, here is a list of resources that I'd recommend for people considering making the change:
Finally, once you're past all the basics, I'd recommend following Andrew's posts as they are highly informative. If you can't get enough of his blog postings, check out his book Microsoft .NET Development for Microsoft Office.