Short but sweet. I recently studied for and passed the 70-510 exam. I utilised the Transcender practice material and found the questions very helpful in not only passing the exam but learning more about the product. I was keen to have my skills in this area recognised before moving on to the 2010 product.
There is no equivalent exam for Visual Studio 2008 Team Foundation Server.
TFS is more than 1 product, it is multiple products. If you think about all of the Microsoft products that are integrated and tested, there a quite a few: IIS, SQL Server, Reporting Services, Analysis Services, Firewalls, TFS, SharePoint, Excel, Project.
There used to be a Microsoft web page you could visit that would show you the number of people world wide who have successfully achieved a specific certification. Where has this gone?