A great blog post here with more information but a snippet below about whats new;

· Remove the need to deploy complex and costly clustering and third-party data replication products for full-scale Exchange redundancy

SCC is a no longer an option and the concept of CCR and SCR get merged into a single availability solution.

· Automate mailbox database replication and failover with as few as two servers or across geographically dispersed datacenters

Granular database failover will be a nice feature since you no longer have to failover entire servers.

· Maintain availability and fast recovery with up to 16 Exchange-managed replicas of each mailbox database

Customers will like multiple replicated database copies since it will more than like steer them away from the need to backup.

· Limit user disruption during mailbox moves between e-mail servers, which allows you to perform migration and maintenance activities on your schedule, even during business hours

I was migrated to Exchange 2010 with my Outlook open and I was prompted to restart Outlook.

· Guard against lost e-mail due to Transport Server upgrades or failures, through new built-in redundancy capabilities designed to redirect mail flow intelligently, through another available route