Exchange 2007 Enterprise Edition supports up to fifty storage groups, one storage group support up to five databases.
Exchange 2007 Standard Edition supports only five storage groups, one storage group support up to five databases.

If You are using Continuous Replication technology Microsoft recommend use one database per storage group.

Exchange 2007 Enterprise Edition supports up to fifty databases per server.
Exchange 2007 Standard Edition supports only five databases per server.

Exchange 2007 Enterprise Edition database size is limited to 16 TB.
Exchange 2007 Standard Edition databases size is limited to 16 TB.

Microsoft recommend limit database size to 100 GB or If You are using Continuous Replication technology database size should be limited 200 GB.

Exchange 2007 Enterprise Edition supports Single Copy Clusters technology (better protection mail system with two Exchange servers and one disc store).
Exchange 2007 Standard Edition do not support Single Copy Clusters technology.

Local Continuous Replication technology (better protection mail store with one Exchange server and two discs store) is supported by Exchange 2007 Standard Edition and Exchange 2007 Enterprise Edition.

Exchange 2007 Enterprise Edition supports Single Copy Clusters technology (better protection mail system and mail store with two Exchange servers and two discs store)
Exchange 2007 Standard Edition do not support Single Copy Clusters technology.

Standby Continuous Replication technology (better protection mail store) is supported by Exchange 2007 Standard Edition SP1 and Exchange 2007 Enterprise Edition SP1.

To use premium journaling You must use Exchange Enterprise Client Access License.