As you might remember I did a blog post on transitioning from a Windows Server 2008 R2 Hyper-V cluster to Windows Server 2012 (well I was using the beta at the time, not the RC yet):

1. Part 1 Upgrading Hyper-V Cluster Nodes to Windows Server 2012 (Beta) – Part 1
2. Part 2 Upgrading Hyper-V Cluster Nodes to Windows Server 2012 (Beta) – Part 2
3. Part 3 Upgrading Hyper-V Cluster Nodes to Windows Server 2012 (Beta) – Part 3

Microsoft has now blogged about the process themselves and they use the migration wizard in Failover Cluster Manager to get the job done where I did this using the Import, “register only” functionality.

This is the first step by step that describes the official way. You can read about the process here:

How to Move Highly Available (Clustered) VMs to Windows Server 2012 with the Cluster Migration Wizard