Hadd is an enigma.
He came quietly, offered some admittedly old ideas, packaged with wide-ranging illustrative examples and "ex. phys. to layman" translation, so that anyone who took the time to read could understand what he was saying. And then he left as quietly as he came, asking nothing and expecting nothing.
Those of you who keep equating Hadd's approach to slow running obviously stopped reading after the first couple of lines. While he states that most people run their easy days too fast, and gives guidelines for how to keep the aerobic running at the right effort, there is plenty of faster running, particularly as the program progresses.
I dabbled with his approach last year, but being a free spirit didn't quite manage to actually follow the details. What I did do, though, was take two things to heart: in the monster thread he suggested that I was probably running too little mileage, and most of it too fast. So I set out to run more, and run (mostly) slower.
I can't (yet) claim any dazzling "oh-my-god" gains, but I did enjoy steady improvement and much better consistency. I ran 10 or 12 races (depending on how you count them), and hit 5 PRs (5K, twice at 5M, half-mary and full-pull). None of them were very big, but still, that's a pretty decent success rate. On top of that, my average race result was a half minute faster than the previous two years. And I turned 38 this summer. To me, that's more telling.
This year, I'm jumping on board all the way. The HRM (goddamn thing) will get strapped on more frequently, and I'll work much more methodically towards specific mileages and HRs. Then, when I'm ready, I'll move beyond Phase I (the monster thread only describes the base phase, or what he called Phase I) into the "sexier" part, and get those 7 or 8 minutes on 26.2 to win JEH's beer.
Based on what I know of how some other people have progressed (CD posted his results on the Lydiard thread, but there are many more), I fully expect to make better gains this year. And then next year I'll be a faster master (eddy, look out!).