This is the best write-up I have seen on Windows Server Essentials 2012 R2 from Paul Thurrott. The guy is a machine for churning out great articles quickly!
http://winsupersite.com/windows-server-2012/windows-server-2012-essentials-r2-preview
For me, the greatest thing coming with R2 is the fact that Essentials is now a role. So many clients we have will make use of this!