GlaxoSmithKline already in January announced they plan tp save up to 30% on their Communication and Collaboration infrastructure costs by moving from Lotus Notes/Domino to Microsoft Online Services.
Forrester created a research paper on this that provides more background. Very interesting read for this still on Lotus Notes :
GlaxoSmithKline is moving approximately 90,000 email users to Microsoft’s Exchange Online, a cloud-delivered service. To make the decision, GlaxoSmithKline (GSK) went through a rigorous internal discovery process to calculate costs, find dependencies, and analyze its workforce. The result is that GSK is able to optimize its messaging and collaboration platform to meet the full range of its end users’ requirements — while saving on its ongoing costs. To make your own cloud-based opportunity, learn from GSK’s experience and: 1) analyze your workforce needs; 2) tier your workforce to optimize costs; and 3) calculate your own fully loaded costs.
Continue at source : Forrester.com