Thanks for this, I think this a really good antidote for the misconceptions surrounding the 10,000 hour rule. Granted, this is still more 'pop science' than actual science/research. And I think calling him 'proficient' with the Uke, is a stretch, I think 'functional' is a better description.

For most of us, we are balancing jobs and real world responsibilities, and can't afford to put in 40 hours a week for 5 years on the long-shot hopes that we would one day be playing our instrument of choice in front of sell out crowds in Carnegie Hall. Realistically, I could afford maybe 1 hour/day of practice (and even that would be a bit of a stretch, probably closer to 3-4 hours/week) which would mean Carnegie Hall wouldn't happen for another 27 years. I think more than anything, the proliferation of the '10,000 hour rule' was very depressing for me, as a small part of the enjoyment of practicing my various hobbies comes from dreaming about the possibilities, and when you break down the numbers, those dreams become highly improbable (i.e. impossible).

I think a better 'rule' would be as follows, largely from my own anecdotal experience and observations with a number of instruments, sports, programming, and other hobbies:

10's of hours = functional; 100's of hours = proficient; 1000's of hours = professional level; 10000's of hours = world class;

As is noted elsewhere in this thread, these numbers are highly variable and dependent on genetics, previous experience, and practice strategies. But I think this is a better way to frame skill acquisition, its a bit more friendly and realistic. I would like to think that after a couple hundred hours of practicing a new instrument, I would be good enough to jam out in front of a small crowd in a shitty bar. And from my previous experience, that has generally been the case.