Yesterday at the PDC, Microsoft gave the world a first glimpse on the new UI for Office 12.
The new UI will have quite a few changes, and you can preview them here:
http://www.microsoft.com/presspass/features/2005/sep05/09-13OfficeUI.mspx
Also check out the Office 12 preview site for more information about the new UI and the new Office open XML formats:
http://www.microsoft.com/office/preview/default.mspx
Don't forget also to look at the Channel 9 interview with some of the Office 12 team members:
http://channel9.msdn.com/showpost.aspx?postid=114720