I have been wanting to post about Exchange 2010 for so long, well today I can. First off you can download the beta here, http://tinyurl.com/c9245l.
One of the best bits for me is the merging of CCR with SCR to provide high availability in what is called a Database Availability Group (DAG). You can have up 16 copies of a database (1 active, 15 passive) spread across multiple subnets.
Storage is another exciting area due to an IOPS reduction opening possibilities to use SAS and SATA for Exchange storage, and combined with DAG maybe even go raidless.
There are many other great new and improved features which I will be talking about over the next few months.
Daniel