John Kelbley’s blog has a recent series of posts (including helpful screenies) explaining everything you need to do a Hyper-V backup is included in Windows Server.
hmm not to labor the point but there is no csv/vss provider available currently so if vhd's on a csv volume you can't use vss to back them up. In other words SAN vss backups don't work, yet!
If you have piles of ca$h for shared storage that's awesome...go ahead and back up your VMs from INSIDE with agents (like you would with a physical system).
If not, use VSS (which you know is part of Windows Server) and pocket the ca$h and use it for a great upgrade or other Holiday Cheer!!!