Just stumbled on this thread while searching for information about using heart rate monitors (HRM) during mountain bike rides. I read some mixed messages above about their utility. I just got one (and a bike computer/GPS) and am looking forward to using it as a more quantitative way to gauge my riding effort and maybe do some training intervals on my mountain bike. My friend told me I would get bored of using the HRM. He said once you know your HR for any given effort, the HRM becomes irrelevant because you can just go by feel and know roughly where your HR is at. I can see some truth to that but I still like seeing the numbers on my bike computer. Am I wasting my time with a HRM?