Pedro Alves, a premier field engineer working for Microsoft has created a very useful Exchange 200x comparisons table. Very useful! The original can be viewed here:
http://blogs.technet.com/sjimmie/archive/2010/05/01/exchange-200x-comparative-table.aspx
Thanks Pedro, good work!
| Feature | Exchange 2003 | Exchange 2007 | Exchange 2010 |
| Exchange Certificate wizards | No | No | Yes |
| EMS Command Log | No | No | Yes |
| Property Dialog Command Exposure | No | No | Yes |
| Role Based Access Control | No | No | Yes |
| Larger and Sequential I/O | No | No | Yes |
| Larger Page Size (32 KB) | No | No | Yes |
| Optimize for SATA Storage | No | No | Yes |
| Continuous Background Online Defragmentation | No | No | Yes |
| Online Background Database Scanning | No | No | Yes |
| Shadow Redundancy | No | No | Yes |
| Incremental Deployment | No | No | Yes |
| Database Availability Groups | No | No | Yes |
| Mailbox Database Copies | No | No | Yes |
| Online Move Mailbox | No | No | Yes |
| Incremental ReSync | No | No | Yes |
| Cluster Continuous Replication | No | Yes | DAG |
| Standby Continuous Replication | No | Yes | DAG |
| Local Continuous Replication | No | Yes | No |
| Clustered Mailbox Server | Yes | Improved | DAG |
| Storage Groups | Yes | Yes | No |
| Recovery Storage Group | Yes | Yes | Recovery Database |
| Exchange Management Shell | No | Yes | Yes |
| Messaging Records Management | No | Yes | Yes |
| Transport Rules | No | Yes | Improved |
| Disclaimers | No | Yes | Improved |
| Multi-Mailbox Search | No | No | Yes |
| Legal Hold | No | No | Yes |
| Personal Archive | No | No | Yes |
| Federated Sharing | No | No | Yes |
| Calendar Repair Assistant | No | No | Yes |
| Moderated Distribution Groups | No | No | Yes |
| Mailbox Folder Permissions Management | No | No | Yes |
| Send Mails to Recipients from EMC | No | No | Yes |
| MailTips | No | No | Yes |
| Moderated Transport | No | No | Yes |
| End User End-To-End Message Tracking | No | No | Yes |
| Transport Rules Integration with AD RMS | No | No | Yes |
| 64 Bit Architecture | No | Yes | Yes |
| Routing Groups | Yes | AD Site Routing | AD Site Routing |
| Administrative Groups | Yes | Universal SG | Universal SG |
| Intelligent Message Filter | Yes | No | No |
| Link State Routing | Yes | No | No |
| Routing Objects | Yes | No | No |
| Network Attached Storage | Yes | No | No |
| Exchange Installable File System | Yes | No | No |
| Event Service | Yes | No | No |
| Recovery Storage Group | Yes | Yes | No |
| ADUC Exchange Extensions | Yes | No | No |
| Mailbox Merge Wizard | Yes | No | No |
| Recipient Update Service | Yes | No | No |
| iSCSI Support | No | Yes | Yes |
| HT & ET Anti-Spam Agents | No | Yes | Yes |
| NNTP PF Access | Yes | No | No |
| IMAP4 PF Access | Yes | No | No |
| NNTP | Yes | No | No |
| Monitoring and Status Node | Yes | No | No |
| Message Tracking Centre | Yes | ExMFA | ExMFA |
| Mailbox Recovery Centre | Yes | ExDRA | ExDRA |
| Mailbox Management Service | Yes | MRM | MRM & RP |