Microsoft IT's Devin Murray is interviewed here on the use of VMM inside Microsoft during the beta. Microsoft IT runs the compute utliity on more than 17,000 servers that provide computing power to 550 buildings across 98 countries from the data center. They use the SPEC benchmark as the raw computing metric in the business conversation. For example, you want to buy a platform with 200 compute units, but you're replacing a system with 40 units that you're not really using fully. You're using 20% of your existing system, but you want to upgrade by 400%. Microsoft IT is changing the conversation to why you want to replace the system and what you're trying to do.
Microsoft IT has ~ 1K production and 500 development applications running on around 70 hosts. The average consolidation ratio is 8 VMs to 1 physical server in the production, and about 16 to 1 in test/dev environments. Their goal..."all new applications to go into the virtual environment..."