Here is an article on Sunray that is very direct and to the point. The argument isn't so much the technology used to deliver a desktop to an employee, but where the true costs are: The management of it.
How much money would be saved if all that was needed was an individual that could simply hook up a keyboard,mouse, monitor and a network connection? All of the hard administration could be handled remotely with a virtual desktop environment. The travel time of an experience technician can be spent fixing the problem, not going from point "A" to point "B". Time to Resolution could be much shorter when there is a problem.
Additionally, what if you could get 10 years of life from a desktop deployment and simply refresh the servers only. Think about how "green" it would be not putting all that equipment into the scrap yard. Let's not talk about the thought of corporate data being put out on the secondary markets with out having the cost associated with scrubbing the disk drives, if that was even a consideration.
Read this article I found on ZDNet Costing Sunray's vs Wintel
The author did a really good job outlining the true costs and overall savings. If you want a very "Green" approach to business computing, with a security model that prevents corporate data from ever really leaving the datacenter in a controlled manner, then this is a good read.
We at Horizon Systems have specialized in Sunray deployments and architectures for 7 years now. We use this technology day to day in our own environment. Mixing it with a virtualization and/or a VDI solution, such as from VMWare, Citrix, Microsoft, and Oracle can put a positive spin on how applications can be delivered to the desktop!