There is a document on microsoft.com/downloads called Guidance for Microsoft Online Services Multinational Customers is not what it seems. You don't have to be a multinational to be interested in the details such as latency stats between you and the BPOS data center. In addition, there is an online ping tool that will tell you your latency between the browser and any of our data centers and provides guiance for whats acceptable.

Add this to your list of BPOS technical reference materials

http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=c4ec4bbe-5979-4cf2-bac5-d86e1baada2c