Maybe I'm just ignorant compared to the average drooling Carmack-worshipper, but I learned several things about the C-man that I didn't know before. For example, I knew that he was a graphics god who had come up with all softs of amazing techniques, such as the software pixel shaders in Q3A, but I didn't know that one of his techniques was so revolutionary that it inspired dissertations and became known as "Carmack's reverse."
The article is an entertaining read regardless, but in case you needed an excuse, there's a few interesting tidbits that aren't about Carmack per se. Basic licensing terms for the Quake III engine are discussed, as well as Microsoft offering a fat pile of money if id delays Doom III until an XBox port is done. Anyway, enough babbling, just go read it. Good stuff.