From The Operations Manager Team blog:
Updates to the Exchange Management Packs for Operations Manager 2007 are now available on the Management Pack Catalog.
The Exchange 2003 MP update includes an improvement to topology discovery that removes the requirement to have an agent on all Exchange servers in the organization in order to see the Exchange topology view. There were also discovery updates, plus a number of improvements focusing on on view consistency, knowledge, script behavior.
The Exchange 2007 MP for OpsMgr R2 update fixes issues with synthetic transactions running on clusters, clearer presentation of data generated when running the Exchange BPA, as well as clearer alerting in the case where MP discoveries are failing due to missing Exchange permissions.