In addition to bug fixes, the Exchange 2013 version, on the other hand, includes new functionality. In particular, the ability to define how many AutoReseed volumes you would like in your design and mailbox space modeling. You can view what changes have been made, or download the update directly.
Mailbox space modeling provides a visual graph that indicates the expected amount of time it will take to consume the send/receive prohibit quota assuming the message profile remains constant. As you can see from the example below, if I start with a 2GB mailbox with a 200 message profile and allocate a 10GB quota (and assuming no deletes), I expect to consume that quota in roughly 22 months. Hopefully, this feature will allow you to plan out storage allocation more appropriately moving forward.
Read more at source: http://blogs.technet.com/b/exchange/archive/2014/10/22/come-get-your-calculator-updates.aspx