A new management pack for Exchange 2007 on OM 2007 has been released.
The Exchange Server 2007 Management Pack includes rules and scripts to monitor and report on performance, availability, and reliability of all Exchange 2007 server roles including Mailbox, Client Access, Hub Transport, Edge Transport and Unified Messaging.
The Exchange Server 2007 Management Pack for MOM 2005 topics explain how to monitor and maintain messaging resources.