According to TechCrunch "Google just took away one of the world’s largest Outlook/Exchange installations for 1.5 million students at Australian schools, and replaced it with Gmail".

<<The cost savings are substantial. The Outlook/Exchange platform involved a AU$33 million contract and took four years to go live. The Gmail/Google Apps rollout, which is being completed by subcontractors, will cost just $9.5 million and should be live by the end of 2008.

This is being called the largest single deployment of Gmail in the world.>>

http://www.techcrunch.com/2008/06/23/15-million-australian-students-dump-outlookexchange-for-gmail/