Certainly food for thought. I think the author underestimates just how bad some programmers are, though. To me, his assertion that there is some arbitrary limit on the productivity differential between any two given programmers is much harder to prove than the assertion that there exist some programmers who are 20x better than others.
There are definately some programmers who are 20X better than others, but I think the authors point was that the 20X difference is between programmers who are 3X above average and programmers who are multi-X BELOW average. The myth is that there are some super-coders who are 20x better than your average decent programmer, and I think that would be difficult to substantiate.
