Up to version 3 now! - hard to believe I’ve been working on this project on-and-off for since 2005. The major changes since 2.5 (release in April 2010) have been a large refactoring of the low-level APIs and scripting APIs. The changes in these low levels were about performance, API simplification, and aligning to the appropriate code idioms you should use when controlling Visio via managed code.
I’m still in the process of creating and updating documentation and screencasts. In the meanwhile, if you want to get started look at the unit tests for VisioAutomation.Scripting.
For those of you who were familiar with the VisioPS and VisioIPy tools, both were significantly updated and in particular VisioIPy usage is quite different than before. These are experimental tools so I don’t feel too bad about changing how they work.
Users of Visio Power Tools should notice any difference besides an improved color picker.