I love Rick Andersons passion when it comes to Windows Mobile. For those in enterprise I thought I would copy in on a recent email from him:

why not

  1. eliminate extra hardware and complexity in your network
  2. deliver the same functionality to end users
  3. have a wider range of devices
  4. reduce unnecessary cost in your organisation

The TCO for Exchange Direct Push vs. BlackBerry is simply better on every case that has seriously investigated it. And if the issue has been about an "all you can eat data plan", well as we know this is about to be addressed by Telstra. 

iT News

MWC: Telstra to launch email service for Windows phones

Telstra will launch an all-you-can-eat mobile e-mail service based on the Microsoft Exchange platform in May

[Suspicious of Microsoft spin then] build [your] own business case with all the figures.

Windows Mobile ROI  and Compete calculators

https://roianalyst.alinean.com/microsoft/mobile/launch.html

For case studies in Australia, see here