Please click the following linsk from Tech Ed 2007 to get more details about Exchange Server 2007:

Erik Ashby on tools to migrate to Exchange Server 2007 
Charlie Chung on Exchange 2007 SP1 Transport
Becky Benfield on Exchange 2007 SP1 Standby Continuous Replication (SCR)
Brent Alinger on Exchange 2007 RTM and SP1 Setup 
Kristian Andaker on Exchange 2007 SP1 OWA improvements