Lionbridge have been working with Microsoft virtualisation technologies for a good long while now, and have just released a case study explaining it all.
Lionbridge have created a Virtual Cloud Lab using Hyper-V and System Centre and give secure, global access to it using Windows Server 2008 Terminal Services. Lionbridge reduced hardware costs by 80 percent for its virtual LAB environment, standardized its testing environments, accelerated machine provisioning, and enhanced security and business continuity.
The lab itself is in Boston and is currently 9 servers running around 300 virtual machines – this will reduce down to 6 physical servers in the not too distant future. They use the Self Service Portal feature of System Centre Virtual Machine Manager to dynamically deploy new environments without any input from the local IT staff.
It really is a great case study, I encourage you to read it.