Update - The MS Exchange Team blog has also published info on SP1. The timeline is still around Longhorn Server release. You can find the info here.
- S/MIME controls for Outlook Web Access
- Personal distribution lists via OWA
- Outlook Web Access monthly calendar view
- Custom fields visible in the OWA address book
- Rules wizard for OWA
- Move-Mailbox cmdlet will import/export from a PST file!
- Bulk mailbox operations (I'm assuming this means creation)
- Public folder management from GUI
- POP3/IMAP4 configuration management from GUI
- IPv6 support
- Support for Longhorn server
- Standby continuous replication (SCR)
- Log shipping on private networks
- Information Rights Management (WRMS integration was pulled from E2K7 right before RTM)
- Improvements in geographic CCR clusters
- Improved VOIP security
The timeline for the release is after the Longhorn Server release
(So we will have to wait for this and the Viridian release before we can virtualize Exchange 2007). Read more at Jim's post.