I've seen demos of Team System and we've got a small version of the Beta installed at work to "play around" with. It looks VERY promising.
The new XNA version of Visual Studio builds on Team System. The extra features look mostly tailored to the content portion of Game Development. Most visual studio projects do not have much in the way of content. Maybe some images or other resources, typically embedded in the DLL/EXE or included as support files. Game development is very big on content and, from what I understand, a major headache to manage.
Developers have good tools for managing code changes - version tracking, a library, merge capabilities, etc. But the content portion of a project is hard to work with. There are a couple of other game content/code products out there so I guess MS is just trying to edge into that area. Makes sense now that they have the XBox product.
Along with Team System, this sounds promising for Game Developers in a team - not so important for single developers, the hobbyists. Team System integrates bug tracking, source control, task items, etc. into one environment.
-ner