With the new Microsoft Office 2007 interface, some people and companies surely stayed with Office 2003 or earlier just because of the drastic interface change. Microsoft also introduced the new docx xlsx pptx and so on formats for the files and that will keep people unhappy because there is no direct backward compatability (although you could install an addon that would do that). There is probably a good reason for not switching to Office 2007 because the company staff will need to be re-trained for the new interface. It's not very much intuitive and self-explanatory. Well there is another company that developed an additional tab for office 2007 that brings the functionality of the classic menus:
IMHO: Microsoft lost quite some market because they didn't implement this feature. Is the ribbon control really that good? Well, the time will show. I am glad Adobe didn't switch to the ribbon interface with CS3.