Found this VERY interesting read on the state of VDI:
Virtual Desktop Infrastructure (VDI) is not a product. You can’t call up a company and ask for 5 licenses of VDI. It is concept comprised of multiple solutions or products to achieve a Virtual Desktop Infrastructure (though recent announcements have Citrix XenDesktop as a single product that comes very close). The concept of VDI virtualizes desktops operating systems (Vista, XP, Linux, etc) and deliver the remote view of the desktop via a display protocol. In addition, there will be management and control systems to manage the provisioning/deprovisioning of virtual machines and applications.
All in all a comprehensive look at some of the players, the concepts and a comparison. If your looking to understand a little more about remote desktops this is a read for you.
update: Forgot the link! Here it is now: The Current State of VDI (Virtual Desktop Infrastructure (Thanks Stephen)