Exchange 2010 SP3

Exchange Server 2010 SP3 has now been released; benefits are:

Exchange 2013 Coexistence supportYou must install Exchange 2010 SP3 if you want to run Microsoft Exchange Server 2013 in a coexistence mode. You can't perform an in-place upgrade from Exchange 2010 to Exchange 2013. However, you can install an Exchange 2013 server into the existing Exchange 2010 organization after you install Exchange 2010 SP 3.

After you perform this procedure, your organization will be running in a coexistence mode. You can maintain this mode indefinitely, or you can immediately complete the upgrade to Exchange 2013 by moving all resources from Exchange 2010 to Exchange 2013, and then decommissioning the Exchange 2010 servers. For more information about how to upgrade to Exchange 2013, see Upgrade from Exchange 2010 to Exchange 2013.
Sent Items Management feature
Exchange 2010 SP3 introduces the Sent Items Management feature to Office Outlook Web Access (OWA). The Sent Items Management feature provides control over whether an item that is “sent as” you, or “on behalf of” you, is copied to your Sent Items folder and to the sender’s Sent Items folder. Before Exchange 2010 SP3, messages that are “sent as” you or “on behalf of” you are copied only to the sender's Sent Items folder.
You can configure the Sent Items Management feature in OWA on the Options page. After Exchange 2010 SP3 is installed, the Sent Items Options settings will be available on the Options page in OWA. (This was included in a previous CU, hopefully its working now!)

Windows Server 2012
Exchange 2010 SP3 can be used together with Windows Server 2012. For more information about operating system supportability, see Exchange Server Supportability Matrix.
More information can be found here; download SP3 here.
(Going on previous experience unless you need SP3, wait a few weeks just in case.  The reliability of recent CU’s have been less than stellar)

Update - Exchange 2013 co-existence requires Exchange 2013 CU1 which is scheduled to be released Q1 2013 (doh!).

More information can be found here;