How to check a VIObject's status

I am planning to write a PowerCLI script to do cold-migrate of VMs.  Move-VM will fail

if a VM is not completely powered off.

My script looks something like this:

------------

$vm = get-vm $vmname

if ($vm.PowerState -eq "PoweredOn") {

    Shutdown-VMGuest -VM $vm.Name

}

<Check guest OS or VM state here>

Move-VM -Destination $newhost

--------------

I can call get-vmguest to check the state of the OS.  But OS shutdown takes time.

I don't want to keep calling get-vmguest every minute, for example.  What is the

correct or better way to assess the VM state before I call Move-VM?

Thanks!