Just as I start getting up to speed with WF4.0 MSDN magazine publishes an article detailing what's new in WF4.5. It looks like there's a lot of good stuff coming but the main thing that I noticed was that v4.0 requires full-trust to run. That shouldn't be a problem for the project we're intending to run workflow in, but if it will run in partial trust in the next release that will open up it's usage for many other applications.
Mocking controllers for WebApi2 - http://www.asp.net/web-api/overview/testing-and-debugging/unit-testing-controllers-in-web-api
8 months ago