Re: Agents of SHIELD. Season 1 Discussion Thread
And, okay, Coulson did say a bit more about Extremis: "It's new. Completely unstable."
Which might seem a little strange, if we assume that the implication of the end of IM3 holds and Stark has actually figured out Extremis to the point where it's kind of stable. He even seems to think he could have figured it out in 1999 if he had applied himself then.
Just walk away, and there will be an end to the horror.