MSExchange Team has just blogged about RU1 for Exchange Server 2010 SP1. They also stated that they are going to release RU2 in early December.
Earlier today the Exchange CXP team released Update Rollup 1 for Exchange Server 2010 SP1 to the Download Center. The release of the rollup via Microsoft Update will happen on October 12th.
This update includes new fixes for the following server roles:
- Client Access
- Edge Server
- Hub Transport
Read more at source: http://msexchangeteam.com/archive/2010/10/07/456538.aspx