There's new news about VSTO this week: there will be a March 2006 CTP version of VSTO "v3" available. It works with Office 2007 Beta 1 TR, so you have to be on the beta program and using the TR build to use it.
There will also be a CTP for the public beta of Office 2007 (beta 2). For a good overview of what's going on with VSTO, Eric Carter has a summary posted on his blog here: http://blogs.msdn.com/eric_carter/archive/2006/03/21/556796.aspx
Visual Studio Tools for Office “v3” – Community Technology Preview now available! You can preview the first CTP of the next version of the Visual Studio Tools for Office. This CTP enables developers to take advantage of some of the new 2007 Office system features, such as the new UI (“ribbon”) extensibility model, and the new Office Open XML file formats. To learn more and to download this software, visit the “Visual Studio Future Versions” page at http://msdn.microsoft.com/vstudio/future/default.aspx.
You will need to separatly acquire a copy of Office 2007 Beta 1 Tech Refresh in order for this version of VSTO v3 to work. You can only get the Office Beta through one of the NDA protected beta programs.
Christin Boyd | Technical Evangelist | Microsoft Corporation
The Office 2007 Beta 1 Tech Refresh version is 12.0.3820.100* depending on which application you open. For example, if you open Help\About in Outlook you will see the version ends with 1002, but if you open Word, you see 1003, and some of the products end with 1004. The setup file should be labeled 12.0.3820.1004.
I hope this post provides more clarity than confusion :-)