With the end of mainstream support for Office 2003, it's tempting to retire Office 2003 from a managed network altogether (and replace with Office 2007, in our environment), but there are pockets of resistance (e.g. users who contractually share Access 2003 databases with large consortia internationally). Security is an effective rationale to compel users to upgrade, when it's defensible.
Does Office 2003 represent a security threat on a managed network, due to end of mainstream support?
EDIT: Much of our user base, and our back end, are moving to Office 2007 for Exchange and Sharepoint integration advantages - so sticking with 2003 in general is not the plan, and heterogeneity is a pain.