With Office 2003 Microsoft has done a big work on user interface's improvements (Office 2003 has really a nice look, actually the "de-facto" standard for the windows applications), but with the future Office 2007 the work actually done is really impressive!!!
Jensen Harris has published today a wonderful preview that I want to propose here for my readers:
Word 2007 - Click to enlarge picture
Excel 2007 - Click to enlarge picture
PowerPoint 2007 - Click to enlarge picture
Outlook 2007 - Click to enlarge picture
Access 2007 - Click to enlarge picture
Word 2007 Ribbon - Click to enlarge picture
Excel 2007 Ribbon - Click to enlarge picture
PowerPoint 2007 Ribbon - Click to enlarge picture
Table Tools in Office 2007 - Click to enlarge picture
Diagram Tools in Office 2007 - Click to enlarge picture
I think that the images gives you the exact idea of the work done... the look is a pleasure for the eyes and the "Ribbons" (the new concept for the Office menu) is always more poweful (more rich than the Beta 1).
With Vista and Office 2007, Microsoft has reached a level on UI design that was totally unbelievable. Great work guys... 