Looks like there is a bit of a distributed thread starting up around the dogfooding of VSTS at Microsoft and the impact that has on design decisions that go into the product. The root of the thread is this eWeek news article by Peter Coffee.
Rob Caron hit the nail on the head when he said TFS is a flexible platform when it comes to supporting processes but I would like to take time to point out (as Peter Coffee did) that Microsoft produces an extraordinary amount of software, and given the level of production it is at a very high quality (compared to what I’ve seen some people who spout the opposite produce).
I remember on many occasions wanting to understand the Microsoft software engineering process better and in many cases I wanted to scale down and emulate it in teams that I have worked with. If we look at the history of the development of Windows from a source management/development point of view you can see just how many hard lessons they have learned both in terms of the requirements they have for their tools and also the processes they need to ensure they ship quality products.
It is important for Microsoft to embed their requirements into their own products to give them that industrial strength edge (just look at the scalability reports) but also scale down to your average development teams size, which I have seen TFS do first hand.