When the ribbon works, which is most of the time, it's pretty good.
When not, it can be a complete PITA. A few years ago I tried to change the scaling of an axis of a chart in Excel from linear to log, and it was so convoluted that I had to look up in the help each time I did it.
I guess the relevant question is whether this would have been easier if the ribbon didn't exist, and you had to do it through the menu bar.
It appears to me that the issue here is that Excel makes scaling the axis of a chart convoluted. Not that the ribbon makes it harder than the regular menu bar.
When not, it can be a complete PITA. A few years ago I tried to change the scaling of an axis of a chart in Excel from linear to log, and it was so convoluted that I had to look up in the help each time I did it.