Q: I have virtual machines running on Windows Server "8" Beta and want to move to the Windows Server 2012 Release Candidate--what do I need to do?

A: The good news is very little! With the new ability to import virtual machines (VMs) in Windows Server 2012 Hyper-V, even when the VMs weren't exported first, the process is quite simple (this is assuming clustering isn't being used, which would require migration of VMs):

It's possible to also import from Windows PowerShell. However, using the GUI does some automated fixing, which doesn't occur when using the Import-VM PowerShell cmdlet, unless you use the Compare-VM cmdlet as well. For example, here are two cmdlets in action, along with resulting output:

PS D:virtuals> import-vm -path 'D:VirtualsAPPVSequenceVirtual Machines8FE19B75-7C0F-4B8E-821E-8A7B06E11938.xml'

import-vm : Unable to import virtual machine due to configuration errors. Please use Compare-VM to repair the virtual
machine.
At line:1 char:1
+ import-vm -path 'D:VirtualsAPPVSequenceVirtual Machines8FE19B75-7C0F-4B8E-82 ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [Import-VM], VirtualizationOperationFailedException
+ FullyQualifiedErrorId : Microsoft.HyperV.PowerShell.Commands.ImportVMCommand

PS D:virtuals> $report = compare-vm -path 'D:VirtualsAPPVSequenceVirtual Machines8FE19B75-7C0F-4B8E-821E-8A7B06E11938.xml'

VM : Microsoft.HyperV.PowerShell.VirtualMachine
OperationType : ImportVirtualMachine
Destination : SAVDALHV01
Path : D:VirtualsAPPVSequenceVirtual Machines8FE19B75-7C0F-4B8E-821E-8A7B06E11938.xml
SnapshotPath : D:VirtualsAPPVSequenceSnapshots
VhdDestinationPath :
VhdSourcePath :
Incompatibilities : {33012, 33012}

PS D:virtuals> $report.Incompatibilities | Format-Table -AutoSize

Message MessageId Source
------- --------- ------
Could not find Ethernet switch 'b8c09ad6-7514-4dd7-a050-1c2eb70ec717'. 33012 Microsoft.HyperV.PowerShell.VMNetwo...
Could not find Ethernet switch 'b8c09ad6-7514-4dd7-a050-1c2eb70ec717'. 33012 Microsoft.HyperV.PowerShell.VMNetwo...

I can see that the problem is that the Ethernet switch in the VM configuration doesn't exist. I would then take steps to fix the problem and then import. This example also shows that it's much easier to work from the GUI, rather than by using PowerShell.