Now Azure just needs to hurry up and release .Net 4.5 on their servers. Until then no MVC4 ,WebAPI, or Entity Framework 5.
Scroll down to New Features for a list of changes: http://www.asp.net/whitepapers/mvc4-release-notes
Scroll down to New Features for a list of changes: http://www.asp.net/whitepapers/mvc4-release-notes
FYI .NET 4.5 will be supported in all roles later this month.