Jack has been coaching me for two years and I've had steady improvement the entire time. With his system you really have to understand what each workout is designed to accomplish. He gives precise paces, durations, and rest intervals that give you guidelines in order to pace yourself. After a while you understand the intensity that each pace represents and you can get away from the watch and the charts. In the beginning I'd recommend following the prescribed paces very closely so you understand what level of intensity is involved. Also, be very conservative in estimating your VDOT. Don't base it off your PRs unless your in PR shape. You also have to account for being tired on high mileage weeks. One of the things that I like most about this system is the lack of ambiguity in pacing. I know exactly what to do if given 4 miles threshold + 2 x 2 miles threshold. I know the rest is always one minute per mile of threshold running and I know the intensity of effort that threhold pace represents. Compare that to so many coaches that say things like 6 mile tempo run comfortably hard. What does that mean? How do you know if your getting the most out of that workout when its so poorly planned. In the end, progress is measured by getting the most out of your workouts. Why would you suffer through such pain if your not getting maximum benefit? That's my JDRF summary. Start with a conservative VDOT, run the paces, read and understand the theory.
Oh, one last thing, the easy pace is a maximum effort, as in not to be exceeded. You will have a challenging time running all the easy runs at that pace, so slow down and recover.