Prepare to be "Ribbonized"
Corporates are still fighting the move from Office 2003 to 2007, predominantly due to UI changes AKA “the ribbon bar”.
In Office 2007 the ribbon was only present in Microsoft’s core Office applications, namely Word, Excel, PowerPoint and Outlook. The Office 2010 release will extend this to Visio, Publisher and no doubt Project.
Speaking from personal experience I have certainly had to tread carefully when pushing central Office system updates, our approach was to upgrade Outlook first (in my opinion the easiest ribbon jump of the 2007 suite).