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All those reasons boil down to "I don't like it cause its different".
In all honesty, that is a valid response. If you take the time to gain a level of competence with things one way, of course you will not be as comfortable with something designed completely differently. The question that comes next is is there enough benefit to the different way to make it worth learning? I have yet to meet a single person who has taken the time to learn 2k7 that does not absolutely love it. Im not the biggest office user personally, but I really hope MS extends the ribbon ui to their other products that have an insanely complex toolbar/menu system (like studio).