At work we migrated our 2.0 solution from Visual Studio 2005 to a Visual Studio 2008.
I have successfully migrated myself some pet projects (both library projects and web application projects). I had not tested migrating Visual Studio Tests projects since I don't use them myself, preferring the faster, more stable and extensible NUnit.
First surprise while converting my work solution: Visual Studio Test Projects were giving us problems while converting. I found some information on how to manually!! convert the projects. I simply could not believe that a raw test project cannot be converted straight away and that some manual steps need to be performed.
Again, it's not an advanced usage scenario that could have sneaked away from QA. It's plain and bloody direct conversion of one project created with one version to the other!!!
That, summed up to all the usual complains for Visual Studio Test (sloooooow, clumsy test runner, close to non-existent extensibility,...) lead us to move away from it and embrace NUnit.
Sad but very true: multi-million company after 2 versions cannot get even close to some years old OSS software.