Its refreshing to see that he focuses on integration testing. Most programmers I know understand that in any kind of engineering every decision is a tradeoff. So testing every line of code means you are trading off speed and flexibility for very little gain in some cases (80/20?). XP introduced the idea that there isn't a tradeoff. You take things to the extreme. So as a methodology its not a good one to follow. But as a force it was absolutely beneficial. There were plenty of moderates arguing against the whole waterfall thing for years and getting nowhere. XP recognised (conciously or not, I don't know) that the zealots who enforced waterfall weren't the brighest so there was no point in putting subtle arguments to them. They would only move to something that was a bit boneheaded. And so XP as a force actually managed to move a lot of the industry more twoards the centre.