Alternative explanation

You may be correct that organisation that formally review the service of their IT department are more likely to adopt Vista.

If this is so then I suggest it may be more to do with the IT department needing to please the oversight committee members than any need to provide direct business benefit.

IT oversight committees are often made up of non IT managers from across the business. These people are the target audience of every vendor's marketing department. They consequently have a better appreciation of what is 'hot' than that which is useful.