With the recent launch of Visual Studio 2012 (and TFS 2012), I have been getting many questions surrounding the upgrade process from 2010 to 2012.
First, some background. There is a good interop story here where you can continue to use VS2010 and connect it to TFS 2012 (and vice versa). You would obviously lose some functionality that is built between the two, but overall it works well. The key here is you can upgrade your TFS environment now to 2012 w/o forcing your clients to upgrade. Since the change is on the server side, you can do this now, and then work on upgrading your clients as necessary.
Overall, the upgrade process is much smoother than in the past. the 2008 to 2010 upgrade was not as smooth as we would have liked, but the same is NOT true with the latest edition. TFS 2010 to TFS 2012 is a much less painful process. Now, as with anything, the more you customized things, the more you have to account for, but overall its a straight forward process.
This site really breaks it down into step by step with great graphics through the whole process.
In addition, lots of great TFS resources / information in general can be found on the TFS homepage.
For those of you migrating from VSS still, there direct migration tools available on our site as well. http://msdn.microsoft.com/en-us/library/vstudio/ms253060.aspx#features This site walks through the various tools and considerations when going through the migration from VSS to TFS.
One last thing for you folks in Public Sector - In nearly every meeting I have, I inquire about the development process that is followed. I get hands on usually everything, and then usually the comments that there is a desire to utilize more Agile methods, but the inability to do so based on strict agency guidelines. Well, hopefully we have a solution for you. Some bright folks on my team created a custom TFS process template that was designed to help address the need of teams who wish to follow Agile Development methods, yet still report up to a waterfall project approach. If this sounds at all interesting, the full details are on our Codeplex page.