Since I last posted on this James O'Neill has released an updated version of the library for Hyper V. He's now up to 1.00b over on codeplex.
There are a number of additions and amendments which caught me out initially as a parameter name had changed and caused my script to return all the virtual machines rather than just the one I expected... but the library is more complete and now I'm extending my collection of scripts for making the provisioning of test and staging servers more automated I expect that will be very welcome.