Here is a quick summary of major changes in Exchange database

• No more storage groups, databases are configured directly
• Number of databases per server increased to 100
• No more recovery storage group, only recovery database
• Databases are no longer tied to a particular server. This helps in recovering a database to a server with a different name than the original one.

For more information  check the link below

http://msdn.microsoft.com/en-us/library/dd877018(EXCHG.140).aspx