I agree, and IIRC, Garmin has a warning and disclaimer in their documentation stating the HR isn't guaranteed to be accurate, and it's easy to see in a graph th

I agree, and IIRC, Garmin has a warning and disclaimer in their documentation stating the HR isn't guaranteed to be accurate, and it's easy to see in a graph that it's using a moving average. I still use mine a lot, because I'm not too worried about the exact numbers while excercising, and I feel like it's probably okay for comparing against previous activities. That's to say if the watch shows ~180 bpm for 10 minutes on a run, it's probably similar exertion to the last time I hit ~180 bpm for 10 minutes on a run, but I don't trust that it's exactly 180 bpm, and I definitely don't trust the "ramp up" and "cool down" measurements from 180 bpm. As you said, everybody I know who cares about accuracy already uses a chest strap.