Actually there are two difficult steps in learning the editor:
1. getting into it
2. mastery
There is a big span of learning inbetween of course, but the first steps where really hard for me. I had never used a 3D editor, and I was used to selecting tools and klicking in the window to do anything. But after I had read a tut and realized how the editor works basically, other stuff followed quickly.
But some ppl will make dozens of crappy maps with their knlowledge, while a few will learn all kinds of tricks that make their maps stand out, flow well, look good while keeping the polys reasonable...