When installing a new Vsphere environment one gets a 60 trial license, that includes all the bells & whistles of the full VMware suite. Including one of my personal favorites SVmotion. This feature allows one to move a running VM between datastores, very cool. Often during hardware & software refreshes we use this tool, for instance getting a new SAN; VMware even suggests utilizing the trail period to complete these tasks!
Unfortunately, if one upgrades their Virtual Center, IE one already has a 64bit Windows OS running Virtual Center 4.X and one does an upgrade to Virtual Center v5.0 over the top; there is NO trial period! The licenses are required immediately! Bummer! Also if one has only purchased a package, say VMware Essentials, there is no SVmotion capabilities.