As I said, I haven't actually done a study of people practicing for 100 hours, I was making a rough prediction. I think if you make it to 100 hours of concentrated practice, you'll be good enough that the average person will think you're great. Professionals will still critique the hell out of you, because you'll have graduated to "the bottom of the class of people who've spent upwards of 10,000 hours." But if you're capable of putting 100 hours in in the first place, you're probably already motivated enough to put in another other 9,900 and take the critiques seriously.

I don't have a better answer than that at this point.