I was looking for a similar list of changes and, much like you, haven't had much luck. Here is the closest I've come to a list of new features:
"From Scrum 2.0 to Scrum 2.2
- Add the Tags column by default on the product backlog
- Add missing transitions to the Bug and PBI"
Which I found here: http://blogs.msdn.com/b/visualstudioalm/archive/2013/04/04/upgrade-your-2012-process-template-from-rtm-to-update-2.aspx.