Let me throw in my two cents worth on this.
I have a tendency to run too fast on just about all my training runs, so recently I tried using a HR monitor to keep myself in check. I really had to pull back on the reins to keep myself in whatever zone I was shooting for. After a few weeks, I started leaving the monitor at home more and more often but could gauge my zone by effort and breathing. When runnig with my wife, I could even tell when she was running too fast. This morning I did a 3/4 effort run, and I knew right off that my heart rate was lower than usual by 10 beats, so I readjusted my zone accordingly and carried on. The results? I feel great and races are showing stady improvement.
If you've got someone to work with face-to-face, of course you want to learn to run by feel from them. Someone like me, however, has never trained under someone with a good grasp of Lydiard's system. The heart rate monitor is an imperfect teacher but better than none.
Here are my zones:
Jogging, 50% to 65% of max heart rate
1/4 effort, 66% to 75% of max heart rate
1/2 effort, 76% to 82%
3/4 effort, 83% to 88% (which lines up very nicely with Tinman's ATR)
and since this is base training, this is as fast as I go for a sustained run.