Comment by quanticle

And the ribbon was designed specifically because more people find it easier to use, as Microsoft's user research showed.

Not exactly. What Microsoft's user research showed was that people who were unfamiliar with Office found the Ribbon easier to use than the traditional menu bar. They did not test whether the same held true for experienced users. They also did not test whether the Ribbon had a higher "skill ceiling" than a traditional menu bar (i.e. if you take two users, one who is proficient with the Ribbon and one who is proficient with the traditional menu bar, and ask them to complete the same task, who is faster?).

Most of the complaints about the Ribbon came from the audiences that Microsoft failed to adequately test the Ribbon on. Microsoft, as far as I can tell, figured that experienced users would quickly get used to the new UI paradigm and adapt. That was not the case, due to the aforementioned tendency for the Ribbon to "helpfully" move things around in order to put the most recently used tools front and center. This broke many people's muscle memory and, more importantly, inhibited the formation of new muscle memory. It's the latter that was especially galling for experienced users. Changing the UI is bad enough. But changing the UI and replacing it with a constantly shifting toolbar that gives the user no indication as to where their controls nor any consistency with regards to their positioning is intolerable.

Imagine if your car radio shifted its buttons around every time you started it to put the last selected station in the first position.