If you are familiar with the pain that can come when migrating mailbox data between servers you will appreciate https://www.migrationwiz.com.
It is a cloud service charged per mailbox that can hook in to Exchange, Gmail, Hotmail, IMAP and other mail servers and import directly to Exchange Server 2007/2010. It takes care of a lot of work for IMAP migrations such as securely gathering user credentials.
I really like the simple dashboard showing the state of the migration. I also like the option to take multiple passes at a mailbox and being able to on filter date ranges.
Configuration is simple.
1. Enter source server OWA/IMAP address
2. Enter destination Exchange OWA address
3. List mailboxes to migrate, then either it will handle credential gathering or you can specify a super user with access to all mailboxes.
4. Press GO and monitor.