Microsoft has released Exchange 2013 CU9, three months after the release of CU8. Microsoft has made a solid Cumulative Update this time (just like CU8 by the way) and during testing not much issues were found.
There aren’t any new features in this Cumulative Update, and personally I don’t expect any new features anymore in future Cumulative Updates either. All development efforts at Microsoft are currently targeted towards Exchange Server 2016.
The official announcement of CU9 can be found on The Exchange Team Blog, CU9 itself can be downloaded from the Microsoft Download Center, just as the accompanying CU9 UM Language Packs.