the Desktop Vitualization Services are very interesting for Windows-based infrastructures e.g.
* to substitute windows terminal services or
* to centralize desktop-envoironments which were not terminalserver-ready in the past
* to give users a individual desktop
One very important reason to virtualize windows and/or linux desktops are the adminstration costs of a distributed infrstructure.
Desktop virtualization in combination with a thin client infrastructure reduce the administration and maintenance at the user-desktop,
Furthermore a per user software collection, including a per user configurable operating system available on any client device.
I hope that makes it a little bit more transparent