While not directly related, already we have been asked why didn’t Office 2008 adopt the “Ribbon UI” from Office 2007 for Windows.  The answer is actually a simple one: we’ve designed our UI for the Mac.  Mac users (that’s us too!) are very passionate about the very qualities that have drawn us to the Mac and expect no less from Office for Mac.  Simply, Office for Mac is to look and behave like a great OS X application.
— from Welcome to the New Office 2008 User Experience by Han-yi Shaw

That wasn’t really convincing.
Okay, okay: that was pretty wrong.

Today, say hello to the leaked Office 2011 Ribbon:


P.S.: I really hope that all that wasted vertical screen estate will be optimized in the final release.