I read this great article on selling XP to traditional (risk cautious) organizations. It addresses some of the reality vs. rhetoric out there. What really caught my eye was the cost of change curve on page 2. I've always thought of the XP CoC over the entire project cycle vs. the waterfall CoC curve. What he shows here simplifies that to one curve with the x-axis not the project time frame, but the "length of feedback cycle". He writes: "Comparing the cost-of-change "curves." The agile and traditional cost-of-change curves are identical. The difference is that agilists follow techniques that keep us at the low-cost end of the curve."
I like that it applies the CoC curve to all of Agile, not just XP.