This was my first thought, too -- how do you manage licensing fees for Windows virtual machines? My hunch is that the price per CPU-hour will be a bit higher,

This was my first thought, too -- how do you manage licensing fees for Windows virtual machines? My hunch is that the price per CPU-hour will be a bit higher, with the difference going straight to Microsoft. They've been looking for a way to migrate to a subscription-based pricing model for a long time, and this could provide just the test-case they need to gauge the willingness of customers to accept such a pricing scheme.