Who's to say what's one person's fun and one person's not-fun? Is it better to use up a part of your life fussing over exercise numbers, to use it up playing video games, watching movies, reading books, talking politics in coffee shops, or posting to slashdot? That cyclist you're disparaging may look at your hobbies with similar disdain. I used to have a similar attitude about people who listened to ipods while running, and then I discovered escape pod's podcasts -- and now I'm completely hooked on listening to scifi stories while running. There's a reason this is all called "recreation" and not "activities designed to satisfy Kupfernigk's view of what people should do."
But on that note: An HRM can be a great training tool. I recently picked up a garmin 310XT to use as part of training for a marathon (I haven't raced for several years). Used right, the HRM can remind you to slow the bleep down when you're going too fast for training; the GPS makes it easy to run a target distance on new, unmapped courses -- freeing you from the tiny tyranny of carefully pre-planning long runs. And if you want to take a half an hour afterwords and compare your HR vs. pace vs. a month ago to see if your training plan is effective? More power to you. If you don't find it fun, don't do it.