If you'd like to know more about the development of the Ribbon (for Office 2007) I recommend this video from a Microsoft developer conference:
The Story of the Ribbon.
Jensen Harris (from the Office 2007 UX team) talks about the Office team adding multiple different types of UI over the years and their desire to both reduce and unify the mess and make it easier to find how to do whatever it is you're trying to do. (There's an often-repeated piece of trivia that the most requested features in the Office applications are things that are already there, so making things easier to find is a big thing.) He goes into things they tried during the development of Office 2007 and how they ended up with the Ribbon.
I'm not a power user of the applications themselves, but I do work in VBA quite a bit and have kept with Office 2003 because I need to make sure things work in a wide range of Office versions. I only have commercial licenses for 2003 and 2013; most of the machines in the house have non-commercial licenses for Office 2010.