The 2nd edition of Extreme Programming Explained has been out for a little while now and Darrell Norton has been covering it in a three-part series. What I want to know is, what’s changed since the first edition? It would be extremely (yes but it’s the right word here) valuable to know exactly what’s been changed and why. I know that the practice of metaphor has been dropped. Other than that, information to that effect is scant.