Here is how I look at and have discovered about the ribbon:
We have two types of users to Office 2007, the experienced office user and the new user.
Experienced User: "What is this, they moved everything!" "I can't find anything, where are my menus?" Most people do not like change. It is not because the new system is good or bad, it is just different. It gets people out of their confort zone and they have to learn something new. Not all people like to learn new things. They are content with the old way of doing things.
New User: "I hope I can figure this out" "This is different from other applications" These are your people just learning the office applications for the first time. The do not know how things used to be or standards of the past. Everything they touch is a new thing to learn and this is what they will base their Microsoft Office knowledge in.
I have seen from beginner classes that people are picking up Office applications up a little easier with the new ribbon when most things are new concepts to them. There are some menus, but many things are accompanied by icons or visual representation of the action in the ribbon and not just endless text menues and sub menus. I think they learn quicker with the new ribbon.
Previous experienced users moved up through office 97 - 2003 easily as most stuff staying in similar spots and menus got longer and longer as features increased. Many users would really just ask "whats changed?" as they dont use 90% of the expanded features added on with each revision. Office 2007 was a show stopper for all these people as all of a sudden, even the simple users had to learn something new. Not everyone will like the new ribbon, but I think most will warm up to it and find it really is much more efficient and productive then the old long menus. I think menu's worked great in the beginning, but Office has become a massive application with 1000's of features and you have to come up with a better feature management system than just simple long lists.
I myself was a little put off by it at first, but then I found it to be rather useful and effective. This is from my tech support and friends in acadamia experiences. Remember to always look at issues/problems from every angle of all users before you call a new feature or way of doing things bad or good.