So RIM is offering a great deal for prospective people wanting to upgrade to BES 5. If you upgrade to BES 5 before March 31st, 2012 you will get a free PlayBook!
Now if you have a huge BES implementation, this might not be enough time to get a project such as this off the ground, but if you have a smaller implementation, you should be able to easily handle the upgrade.
Why should you be running BES? Well another than the obvious reason of staying up to date with the latest secure code and patches, as well as support from RIM, you should upgrade to prepare yourself for Mobile Fusion.
Mobile Fusion is the software from RIM that will allow you to manage other devices than BlackBerries. This has a requirement of BES version 5.0.3. So upgrade now and get that free PlayBook!