Those of you who have deployed Exchange 2007 on Windows Server 2008 may be aware of an issue involving the backup software that Microsoft includes with Windows Server 2008 where it no longer supports streaming ESE backups. So unless you're using a 3rd party product, you're not able to back up your Exchange servers. Microsoft today announced that they are working on an Exchange-provided VSS-based plugin to Windows Server Backup that will enable the ability to back up your Exchange servers.
If this problem affects you, or you're holding off deploying until a fix is ready, Microsoft says it will be available some time this summer.