As a First answer: nothing at all. I've seen a number of demo's, seen people work with it, read about it and I like it. Quite a nice tool.
My problem is that I cannot work with it myself. I have "Visual Studio Team system for workgroups" edition. Which includes many team server tools. The team explorer and source control do work. Not always that well, in the team I'm working with at the moment the backend is known as "team frustration server". But datadude, the database project addin, does not install on this version of VS. It requires the Team Suite edition of VS. I don't have a license for that and given what I've seen of TFS I'm not sure whether I want one.
Thank goodness, there is still Red Gate. In the past, before the datadude days, their sql db tools have been a great help. In the future they will be as well.