Exchange 2007 SP2 was released yesterday (version 08.02.0176.002). Below is some information regarding this release.
Microsoft Exchange Server 2007 Service Pack 2 (SP2) has been designed specifically to help meet the challenges of any business and the needs of all the different groups with a stake in the messaging system. Exchange Server 2007 SP2 is a mission-critical communications tool that enables employees to be more productive and access their information anywhere and anytime while providing a messaging system that enables rich, efficient access to e-mail, calendar items, voice mail, and contacts. For the administrator, Exchange Server 2007 SP2 provides advanced protection options against e-mail security threats, such as spam and viruses, as well as the tools to help manage internal compliance and high availability needs.
For an overview of the new features that are available in Exchange Server 2007 SP2, see "What’s New in Exchange Server 2007 SP2".
Active Directory Schema Changes: