These are the major changes that can be seen in new Exchange version:(that I can remember 🙂 )
1. No SIS in exchange 2010(Single instance storage)
2. RBAC(Role based access control List.
3. Exchange web control panel.
4. Archive mail box feature
5. The maximum recommended mailbox database size has increased from 200 GB in Exchange 2007 to 2 TB in Exchange 2010
6. Mailbox databases are organization level & should have unique names.
7. DAG (Database availability Groups instead CCR which is no longer present)
8. online Move mailbox
9. E discovery multi mailbox search.
10. MOMT(mapi on middle tier –i.e all mapi communications also go thru CAS).