I’ve found this really useful script:
http://www.peetersonline.nl/index.php/vmware/calculate-vsphere-5-licenses-with-powershell/
You will need to run it using PoweCLI, and it will enumerate your ESX/ESXi sockets, compare them with your licenses and tell you if you have spare vRAM capacity (so you are getting advantage from the new licensing scheme) or you are overcommitting too much by a licensing point of view.