The study I assume you are basing your statement that '[delayed gratification] when measured in children, is correlated with all sorts of positive things' has largely been debunked. When the poverty level of the children tested is factored out, the effect disappears.
It seems what is really being shown is the rational basis in children to discount promises made by adults for future rewards, when in their experience adults had been unable or unwilling to deliver on promises made.
I don't think either of those two links refute the idea that "delayed gratification when measured in children, is correlated with all sorts of positive things".
From The Daily Beast article: "Eigsti does not feel her data disproves Mischel—he was actually a co-author on her paper, and she thinks her work is consistent."
The Priconomics article says: "The original marshmallow experiment concluded that the children's ability to wait for a second treat indicated an innate ability to exhibit self control". But nothing I've read indicates that Mischel believed the ability to delay gratification was innate. In fact, most of his previous research indicated that such an ability was strongly influenced by environmental factors.
It seems what is really being shown is the rational basis in children to discount promises made by adults for future rewards, when in their experience adults had been unable or unwilling to deliver on promises made.
http://www.thedailybeast.com/articles/2010/02/19/just-let-th...
http://priceonomics.com/what-marshmallows-tell-us-about-sili...