The October 2008 issue of TechNet Magazine is full of great articles on Hyper-V. One article in that issue (Backup and Disaster Recovery for Server Virtualization, by Adam Fazio) talks about how Windows Server Failover Clustering can be used in a Multi-Site Cluster to provide business continuity in the event of a complete site loss. I truly believe that being able to automatically move your entire VM from one data center to another in the event of a disaster is one of the features that makes Microsoft's Hyper-V stand out from the crowd.
The article points to the vendors on Microsoft's Failover Clustering -- Multi-Site Clustering page to provide the replication engine that is needed in order to make this work. SteelEye is listed on that page as a Failover Clustering -- Multi-Site Clustering Partner.
Here is a video demonstration of SteelEye DataKeeper and Windows Server Failover Clustering working together to do a quick migration of a Hyper-V VM across different data centers.
The interest in DataKeeper Cluster Edition for Hyper-V HA/DR has been tremendous and we at SteelEye are very excited to be working closely with Microsoft to provide this solution.