This thread is becoming one of my favorites, nice debate !
I’d second what Ryan says I have trained quite a few people, most of them not even "web proficient" and it was a breeze teaching them to use the backend. Remember the backend is dumbed down a lot for a "simple" editor and even a content manager. The full package is another story but quite intuitive nonetheless !
It does not mean we can’t improve usability, we sure do, but it’s not that bad ! And you might have noticed MODx has already undergone nice little touches, like the ability to access a document’s children directly from the document properties tabs, but there are little nuggets here and there. I am quite optimistic about the future GUI, just watching at what getting done by the dev team already

This thread is a nice pool of ideas to get things even further