The Exchange 2010 Beta SDK just released and I wanted to call out that using the Backup and Restore API (i.e. Streaming Backups) is no longer supported.
"Exchange 2010 does not support streaming-style backups. In versions of Exchange earlier than Exchange 2010, backup applications use the ESEBCLI2 interface to perform streaming backups. This SDK does not contain information about the ESEBCLI2 DLL. For information about this interface, see ESEbcli2 DLL Functions Interface."