You said, "You won't need to guess how many licenses you may need at the beginning of the contract term. Instead you can use the Cisco IAC counts to “pay as you grow,” buying licenses at the contract price when you actually need them."

There's another compelling option, the zero-license subscription model. As an example, here's a price comparison of RHEV vs vSphere http://red.ht/1ncq4l4

Perhaps the benefits of each approach depends upon the current use of Linux and the degree of existing virtualization, if any.