Carmack speaks. I am not that up on the Mac world, but I have no reason to doubt Carmack knows whereof he speaks.
For those who know me, there is the understood depravity that I am a fanatic fanboy of John Carmack. He was my inspiration to get into video game programming back when I was writing unix software for the computer science department at Ohio State University. I'll never forget the quote from that first Wired Magazine article (still on the net if you look for it at wired.com... someday I'll have to put a link to it here). Anyway, the quote was something like (I'm paraphrasing):
"Anyone can succeed as a video game programmer if they are willing to put in the hours. 12 hours a day, 7 days a week."
At the time, Carmack was living that mantra. He pretty much lived at Id Software. And as we all know, the fruits of his labors have had a significant impact on the games industry. My idol has since cut back a bit on the hours at the office, and his once myopic focus has since broadened to include everything from rockets to macro economic theory.