I trained with a HRM for a few years and found the biggest advantages to be you get immediate feedback or your real work effort, and over time you'll become more aware of your physical state of being. On training days that I was tired, stressed, or hadn't eaten correctly I'd see a definite increase from my normal heart rate range. After a while I became really aware of my level of effort and stopped looking at it much. Here's a link to an article written by Mark Allen (6 time Ironman champ) about heart rate training......this is what sparked my interest.  http://www.duathlon.com/articles/1460 Great tools, have fun.