In case you haven’t seen or heard the new Microsoft Office 2007 includes a completely overhauled user interface dubbed Fluent. I’m been lucky enough at work to be included in our pilot program. Office 2007 features a new “ribbon” across the top of all applications. It is supposed to be a much more intuitive design to follow. Although there is a learning curve for any advanced Office user, there are reported productivity improvements after that.

Microsoft & Forrester Outlook 2007 Productivity Report

Wikipedia: Fluent UI