Another thought: most of us are not made of the same kind of stuff as Donald Knuth.
Whatever origin you think world-changing inventions or intellectual work has, talent or the right mettle to push yourself extremely hard or whatever, most people do not possess it. I don't. And I think there is much less motivation to "go against the flow" if you are reasonably sure that no great benefit will follow from it.
I have been dabbling with Ruby and other languages for a year, but have never had this sort of discipline. For a couple years I have wanted a programming job but have always had serious doubts about whether I can really "hack it" as a professional. I don't know any programmers personally (well, one friend on the other side of the country in SF, heh), and I look at job openings and their requirements / desired experience all seem so intimidating. :-/
I like graph paper for making vaguely mathematical doodles in classes. I even happened to independently "invent" a few concepts while doing this, like triangular numbers and the polyomino sequence. :-)
Got a print copy of the book two days ago. Worked through most of the first chapter, and really loving it so far.
No CS background and a little (~1 year off and on) programming experience. Though having taken a symbolic logic course in college is definitely making the first chapter easier! :-)