Yup its super simple.....Yes I'm using nfs as my datastore in vmware.
I now have two exact systems at different locations. Basically at each site there is a vmware box and a qnap nas. Each night the entire datastore folder on the main nas replicates to the backup nas using rsync while the vm's are running. At the backup site of course the vm's are powered off awaiting a failure of the main server.
Its been a couple months now and about once a week i power on the vm's at the backup location to check their consistancy, and no issues so far.
I've got 600gb of vm's replicating every night using a 5mbit connection. Working good so far.