Not everyone has reached the same conclusions, however. Computer Sciences Corp. compared the costs of running 5,000 desktop computers with 5,000 VDI instances and found that VDI cost, on the whole, 20 percent less, said Phil Grove, CSC's global director of end user services on desktop virtualization, in a recent interview.

CSC manages about 1.2 million desktops for its customers, including some VDI instances. In some cases VDI can even be faster than desktops, depending on the network and the data center, Grove said. In other cases, due to bandwidth and processing needs, there will be some users who "will always require a workstation."

Microsoft recently with Citrix to offer VDI solutions. But Schuster's post advised only to use VDI in "specific scenarios."

For instance, VDI makes sense in those cases in which workers have to maintain two desktop computers in two different locations. It also makes sense for shift work, when a single PC is shared by multiple employees.

The blog post deflates some of the commonly held assumptions about VDI's benefits for general enterprise use: It is true that VDI reduces hardware costs. But it also increases software costs. It reduces help desk costs, but increases desktop engineering costs as well, the company argued.