I first learned of Apdex at CMG 2006 and led a pilot project within my company to understand how we might use it. I presented my experience at CMG 2007. At that conference, I ran into an acquaintance, Neil Gunther, who had begun working with Apdex and alternate visualization techniques.
Neil has now published one of the most comprehensive discussions I’ve seen on Apdex: The Apdex Index Revealed.