Several years ago I fell into the HR trap and only trained using HR. I've learned that it's all about wattage. HR is is important in other ways, like gaging how tired I am. When doing hill repeats and the like I only pay attention to my output and dissregard my HR entirely. For example I try to maintain 320+ watts for the entire climb. At the begining I might be at 120bpm ( I have a very low max HR 171bpm ) and at the end be at 169. If I worked off of HR I might be at 450 watts a the begining but would be down to 200 watts a the end. I've done back to back tests and my times are much slower when using HR instead of watts.
I hired a coach three weeks ago and the first thing he asked me was if I trained with watts or HR. He was very happy to hear that I use watts as that is the most accurate mesure of how you are performing.