IDC have produced a paper describing the benefits of Microsoft Mobile messaging
The headlines were that companies implementing Microsoft Mobile based solutions:
You can download the PDF here.. http://download.microsoft.com/download/c/7/d/c7d98c4f-5469-49d6-9a76-288e9abe66a9/Mobile-Messaging-Benefits.pdf
Or view online here http://www.microsoft.com/windowsmobile/business/strategy/roi.mspx