>>> The Essential Plus kit allows you to use vMotion, but not Storage vMotion, so I can move my vm's between hosts at will, but cannot move them between datastores.
Yes and no. The Essentials Plus Kit does not include storage vMotion, but you can use "Change both host and datastore" to live migrate VM's to other datastores. This is possible since vSphere 5.1 (see vMotion bug fixed in vCenter server 5.1.0a)
André