Seems that many Gov people will have a Blackberry for work and an iPhone as their "personal" phone.

Also, for what it's worth, it baffles me that Microsoft isn't trying to advertise and push Win Phone 7 as the "best in class" Exchange client. A bit of digging turned up this 2010 article with feature checkboxes and it seems that WP7 actually has fewer Exchange-related features than earlier Microsoft phone products. (Notable for its absence on this chart: no Blackberry...) If Microsoft could do nothing else, I'd imagine they could do really killer integration with their own mail server.