Client virtualization, by contrast, dramatically changes the entire end user value chain delivery. Many discussions of client virtualization focus on the fact that, when done right, the end user sees no difference between his or her screen whether it is delivered via a traditional "thick" client or delivered through a virtualized environment. That is all to the good, and, frankly, if client virtualization imposed a significant difference from the traditional thick client, it would most likely be a non-starter.

However, the method by which that identical screen is delivered to the end user is significantly different in a client virtualization scenario. This means that the processes and operations of delivering the client environment must change—a lot—to achieve the benefits of client virtualization (more on that in a bit).

To begin with, new hardware must be placed in the data center to run the virtualized machines. So the cost of creating the operating environment is a necessary investment to put client virtualization in place.

Second, individual virtualized machines must be created and made available on the new data center-located machines. In other words, there must a migration of the existing physical machines into new virtual machines.

Third, the organization's network capability with regard to capacity and latency must be tested and, if necessary, upgraded to support the flow of data between the client devices and the data center. A network that was previously very capable of carrying the data traffic between thick clients and server-based applications may not be robust enough to carry the increased traffic characteristic of client virtualization.

Fourth, the established processes the organization uses to manage client machines will need to be modified. Simply put, a lot of the work formerly necessary to keep client machines up and running goes away with client virtualization. No more worrying about whether the antivirus software is up to date. No more having to make "truck rolls" (i.e., in-person visits) to figure out what's wrong with the machine. The client environment is created on-the-fly back in the data center and served up fresh each time the user logs in. Some (but not, crucially, all) of this work is displaced back to the data center, which needs to have people manage administration of user environments, updating the images from which new virtual machines are created, and so on.

So, it's easy to see that there is a lot of churn in moving to client virtualization —which is why Gartner's statement should have been "as much as 40% of companies will undertake client virtualization by 2010." To my mind, the fact that four out of ten companies will take on the work I outlined above in order to implement client virtualization indicates that it must offer significant—nay, remarkable—payoff to make that 40% ready to undergo that burden.