Depends on what context you're using it - e.g. for ASP.NET Web Forms and ASP.NET MVC there are a good few blog posts around (though the Web Forms are typically based on v1)
I personally found that I just wanted a thorough end-to-end understanding of what this baby can do... For that, there's no substitute for just downloading the source and reading the tests - they're compact and complete and are bound to teach you a thing or two about writing good tests along the way.
(The maintainers are aware of the pain of the fact that a subset of the documentation is v1 specific, but unfortunately nobody (including myself, blush) has yet stepped up to the plate to do the update)