The Server Role Calculator, which is very helpful for sizing, has now also been released for Exchange 2013. With the Role Calculator it is possible to determine the hardware requirements for an Exchange 2013 organization.
The Role Calculator can be downloaded here:
http://gallery.technet.microsoft.com/Exchange-2013-Server-Role-f8a61780
The Exchange Server 2013 Management Pack for System Center Operations Manager has also been released and can be downloaded here:
http://www.microsoft.com/en-us/download/details.aspx?id=39039