Before editing this post I had said that the ribbon bar takes up too much screen real estate, but actually a side-by-side comparison reveals that with all the tool bars enabled, MyInfo takes up even more space.
But I usually hide MyInfo's favorites bar, so without it, the space is about the same.
You can also save more space by hiding the formatting bar.
I still think that the ribbon interface is bit more crowded, complicated and confusing and doesn't really offer a compelling improvement over the simple menu/toolbar interface which MyInfo currently uses.
If the choice is between MyInfo’s current user interface and the Microsoft ribbon bar, I will certainly keep the current interface. I don’t even need the latter as an option at the expense of bulking up the code.