Thanks for sharing that with us GrimFang. I'm interested in reading this document just as a matter of interest, but I'm having trouble unzipping it - I think there might be an error. Could you check it?
Also, I came across an interesting article which sort of fits in with my general instinct about the time it takes to learn new things:
http://norvig.com/21-days.html
While the points made probably don't apply to all the people all of the time, I find that with my own attempts to learn new skills (especially music) my ability has taken years rather than months to mature, seemingly irrespective of the intensity of the effort applied.