A few weeks ago Matan & I had the honor to participate in  a panel discussing pros&cons of the Team Foundation Server, This panel hosted by Sela & Microsoft at Microsoft buildings (Ra'anana).

Here are some of our thoughts:

• The Centric approach of get all the items (tasks, bugs, impediments, sprints, backlog) in one place and can easily connect to your code, and easily generate graphs from the already entered details - is a great approach and make life easier.
• Adding tests to your code, using the VSTS is easier. Also adding simple automated build and integrate your tests to run on your nightly builds.
• We are now implementing in two separated sites on the same code, and we doing the synchronization by our self.
  Orcas Gonna solve the disconnected server problem.

I am not telling you that this tool is perfect, it is absolutely has its weaknesses but I think that this is a good decision to choose it.