Actually, I agree with their characterization of the agile position. They manage to peer through the rhetoric to uncover the strengths and weaknesses of the agile practices and to then compare and contrast those against the strengths and weaknesses of the plan-driven practices. They go further, and show how to borrow from each in the very many cases when the situation calls for it. This is no small accomplishment. I commend the authors for having managed it, and to make the result readable at the same time.
A word I find interesting throughout their discussion is the word discipline. The concept of discipline runs its separate way through both the plan-driven and agile camps. My Crystal Clear methodology is as low on the discipline scale as I can make it. On the other hand, Extreme Programming calls for high levels of discipline, as anyone who has attempted it can attest. In fact, along with Watts Humphreys Personal Software Process (PSP), I list XP as among the highest-discipline methodologies I know. So we have both low-discipline and high-discipline examples of agile approaches, and plan-driven and agile examples of high-discipline methodologies.
In their thoughtful way, Barry and Rich capture this and inform us that plan-driven and agile approaches lean on different meanings of the word discipline:
[T]he term disciplined, whose dictionary definition includes both common compliance with established processes and self-control, is confined to process compliance by CMM bureaucrats, and confined to self-control by agile free spirits.
They remind us:
If one has strong discipline without agility, the result is bureaucracy and stagnation. Agility without discipline is the unencumbered enthusiasm of a start-up company before it has to turn a profit.
That is, both types of discipline are needed, in varying degrees. Part of the differences between plan-driven and agile approaches comes with highlighting one or the other meaning of the word discipline. Balancing your approach is much about balancing the two meanings of the word. That balancing is one of the things this book describes.
This is an outstanding book on an emotionally complicated topic. I applaud the authors for the care with which they have handled the subject.