After last nights release of new TFS and Visual Studio bits at the Build conference I spent this morning upgrading my demo VMs. Firstly I upgraded to TFS 2012.3 and then snapshotting before going onto 2013 Preview. So by changing snapshot I can now demo either version. In both cases the upgrade process was as expected, basically a rerun of the configuration wizard with all the fields bar the password prefilled. Martin Hinshelwood has done a nice post if you want more details on the process
Looking at the session at Build on Channel9 there are not too many on TFS, to find out more about the new features then you are probably better to check out the TechEd USA or TechEd Europe streams.