I recently did a MED-V project to help remove technical blockers for a Windows 7 rollout. MED-V is a useful tool for corporates to make use of a feature of Windows 7 Enterprise called Windows XP Mode. There's a link to the MED-V product pages below, but the way to think about MED-V is as a creation, delivery and management service for Windows XP Mode images in a corporate environment. Windows XP Mode is a great solution for resolving application compatibility issues with Windows 7, but try managing the Windows XP Mode images when you have more than a handful of users, it's not easy - that's where MED-V comes in.
Microsoft Windows Enterprise: MED-V
Microsoft Desktop Optimization Pack (MDOP) Technologies TechCenter
TechNet: Microsoft Enterprise Desktop Virtualization
The Official MDOP Blog
While working with MED-V I can across a couple of issues that will probably affect most other users of MED-V.
I hope you find this information informative.