I know they put in a new method to sync tasks in PS 2013 that requires Exchange 2013. I also read an artice that said if you deactivate the farm feature "Farm Level Exchange Tasks Sync" it would revert to the 2010 functionality.
I have deactivated, but i am not getting any task syncs. There has to be a method to sync tasks in 2013 using Exchange 2010. It isn't reasonable to expect that you would upgrade your Exchange environment just b/c you upgrade Project Server.
Scott Jones