Gartner published several interesting reports around Microsoft's Desktop Optimization Pack, Software Assurance (SA) and the risk of skipping Vista. These reports are publicly available!

Quantifying the Value of Microsoft's Desktop Optimization Pack
http://mediaproducts.gartner.com/reprints/microsoft/vol4/article6/article6.html

How to Quantify the Value of Software Assurance for Windows Client
http://mediaproducts.gartner.com/reprints/microsoft/vol4/article5/article5.html

Understand the Risks of Skipping Windows Vista
http://mediaproducts.gartner.com/reprints/microsoft/vol4/article4/article4.html

These reports can be used when discussing any of these subjects with your customer.

One of the most often heard difficulties when customers are interested in Microsoft Application Virtualization (App-V) for the desktop, and they do not yet have SA, is that buying SA just for the use of App-V is expensive. In this scenario it's important to show the customer the business value of SA and mdop. This is where the Gartner reports "How to Quantify the Value of Software Assurance for Windows Client" and "Quantifying the Value of Microsoft's Desktop Optimization Pack" can really help.

Additional MDOP selling guidance is available here:
Microsoft Desktop Optimization Pack: Sell
https://partner.microsoft.com/40071975