But why is BPM during workouts so valuable? Sure, I want to know my distance, maybe steps etc, but my iPhone can do that.
I can charge it every day if I want to, but like I said, most of the time it just doesn't bring me the utility to make it worth it.
Heart rate measurement is great for keeping track of your cardio fitness. Before I got the Watch, I tracked walking / running distance on my iPhone, but for the past ~2 years I've had the Watch, the measurement that actually helps me understand my health much better is my heart rate.
When I work out, it's easy to see if I'm hitting my max heart rate, and for how long, then seeing how quickly my heart rate returns to resting, which are all important metrics to know. Even watching my resting heart rate decline from the upper 60's to the lower 50's / upper 40's over the past 6 months is proof that the exercise I've been doing is paying off, at least as far as my cardio / heart fitness goes.
Clearly there are other devices out there that can do similar things, but having the Watch, which I also use for calls, texts, checking emails, weather, podcasts, music while out and about hiking, biking, swimming, etc., and not requiring me to carry my iPhone, it's been an awesome piece of tech.
And this is coming from a guy who previous to getting the Watch, wore my beloved Seiko Automatic watch every day for 15 years and never thought I would give up wearing the mechanical marvel that it is. It's still ticking away, but unfortunately lives in a drawer now and I don't see going back to it any time in the near future. In fact, I'll upgrade from the Nike 5 Watch I have now, which I bought not knowing how much I would like it, to the next titanium version so I get the sapphire crystal and better quality case material, knowing full well it will get worn and used daily.