I also thought it was a great article and thank you for posting it here. Now that I'm teaching my young children math, I'm finding all these areas where my math education was lacking. It surprised me because I always took the highest level classes and have a degree in engineering. Then I read things like the Number Devil, Singapore Intensive Practice, Life of Fred, etc. and think "how did I get through school without being learning some of these things?"
--Poster child for the Calculus Trap grin