When reviewing Chet Hendrickson’s paper on the evolution of Extreme Programming practices, I was surprised that he completely ignored Kent Beck’s revision of 2004. As does Ron Jeffries’ practices representation, by the way.
5 Years of eXPerience resulted in a complete revision of Extreme Programming Explained. The general tone softened, partial adoption became acceptable and the practices were extended, and divided into primary and secondary practices. Maybe Kent considered XP as under-adopted, but I missed the strong and ahead leadership from v1. No compromise. Working software is the goal. Extreme focus. Programming is the way.
I also felt that in the v2 edition, good ideas were introduced, but good practices were also replaced. Because I instantiate Scrum’s engineering standards with 
XP practices in my framework My.Fragility, I decided to merge the best of both:
Note: when checking the original Extreme Programming Installed book myself, I wondered (after all these -6- years!) why it did not mention the Coach role. When moving to Scrum after our ‘pure’ XP application, I kept promoting this role. I still do in my My.Fragility framework (on top of Scrum’s Product Owner, Team and ScrumMaster).
And I still don’t known why User Stories was not an explicit XP practice from the beginning…
When I read the book Extreme Programming Explained, a very central issue for me was the reason why all the ‘extreme’ principles were introduced: to bring better value for the project-customer at the end. I see this as a very core part of all the practices, in the end they all serve for the good of the project and the customer. Perhaps I see this as a bit missing in this graph of the xp practices ?