With my old boss' permission we did an experiment.

We had experienced and inexperienced users complete normal and unusual tasks in both old word and the ribbon.

The data was crazy. It took several minutes more to do normal tasks in the ribbon, and about 30m to an hour to complete obscure tasks. Some tasks were not completed at all. Meanwhile a simple menu yielded results within seconds.

The ribbon is clearly not a good ui.

I AM currious how that experiment would turn out today, after an entire generation has lived with it.