When copying VHD files from one machine to another or re-creating a VM, Windows 2008r2 and 2008 required you to manually grant rights to the VM Specific SID after import to successfully start the VM. The import process wouldn't stamp the copied files with the proper machine ACLs resulting in a "General Access Denied" error. (fix here) Server 2012 seems to have fixed that problem. When importing a HyperV guest to 2012, the correct rights are automatically applied. This is a welcome time-saving fix and thus far I'm very impressed with the Hyper-V improvements in 2012. More to come on that... this is obviously small relative to the major functionality changes, but I'm happy they paid attention to the details as well.