Exchange 2007 is supported in 6.0 MP6, which was posted Feb 26, 2008.
It is also supported in 6.5.1, posted Dec 2007.
In 6.0 MP6, support is limited to legacy Exchange features (ala Exchange 2003-like features). There is no support for x64 Snapshot Client and no support for LCR/CCR (cannot yet backup replica; only backup the primary).
In 6.5.1, x64 Snapshot Client support is added.
Planned for 6.5.2 in CY2Q08:
- LCR/CCR support for backing up the replica
- Instant Recovery from a snapshot
- Email granular restore from database backups