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.
He begins by introducing the Apdex concepts, then spends time discussing some of the nuances, and addressing common criticisms. Next, he introduces a visualization technique using 3- and 4-dimensional barycentric coordinate systems, and wraps up with a review of modifications to Apdex that have been suggested by others.
Neil knows his subject well, and his clear, down-to-earth writing style makes this a pleasure to read. Highly recommended.