If this tool is news to you, basically it allows you to update your VM images while stored in a library to the whatever current patch/service pack release you want so when you deploy them they are at the most current.
Here is some content I borrowed from the CanITPRO blog:
VMST 3.0 helps customers more effectively—and safely—manage the workflow of updating their offline virtualization environment. Using VMST 3.0, customers can now service:
- Offline virtual machines in a SCVMM library.
- Stopped and saved state virtual machines on a host.
- Virtual machine templates.
- Offline virtual hard disks in a SCVMM library by injecting update packages.
- Windows Server 2008 R2 Hyper-V host clusters.

Read about it here: http://technet.microsoft.com/en-ca/library/cc501231.aspx
Join the v3 Beta here: https://connect.microsoft.com/site14