What makes you so sure that your intuition on what is an accurate heuristic for power management is so much better than Matthew Garret's? As a kernel developer that seems to work almost full time on power issues for Red Hat, one would hope that he has a more than passing familiarity with the needs of the enterprise market. If your answer is along the lines of intuition/personal experience, then perhaps you should consider the possibility that your needs are the atypical ones? If your answer is something entirely different, then please elucidate us, because right now it might seem like you're stating opinions as facts.
My somewhat limited personal experience is that most data centers I've worked with have a total power limit per rack that is painfully low, and that reducing power usage by a few watts per system would allow us to stuff in one more server per rack, leading to a significant amount of savings. This resonates well with what Garret is saying.