There was an old blog post comparing pianos to text editors.
A "simpler" piano would only have white keys, but to a piano expert the piano appears invisible (and powerful) after the initial learning curve.
I think an important attribute of mastery is related to consistency over time. Microsoft Word '95 vs 2007 (the ribbon) is a great example.
Mostly MS's keyboard shortcuts have been consistent (Alt-F4, Ctrl-B, Alt-F-S), but their UI has been inconsistent (making mastery harder).
In any case: "tools for experts may seem initially awkward to non-experts"
...and: "initially non-awkward tools may hamper capabilities as the operator skill increases"