Originally Posted by Koyote

I use my Garmin watch when running around town on my commuter bike, since I don't usually keep a computer mounted to that one. And yeah, when I am using a computer, I leave the watch at home and wear a chest strap HRM. So, why did I pay $538 (wholesale cost) for the Garmin watch? Here goes:
1) Overnight data on HRV, Resting HR, sleep quantity/quality/stages.
2) Training Readiness score.
3) Recovery time predictor.
4) And all of the other smartwatch/fitness watch data that you would expect, much of which has been mentioned above.

For me, 1-3 above have had the largest impact on my training quality and overall fitness of anything I have purchased or done in years. In particular, the overnight data showed very clearly the effect of alcohol on my body (as well as late-night screen time and snacking), which led to dramatic behavioral changes: within a few months of purchasing the watch, I had cut my alcohol consumption about 95% -- which, within about four months, saved me more money than I had paid for the watch. At this point, I have (at most) 1-2 drinks per week and am considering quitting entirely.

Bottom line: If my Garmin watch broke or was lost today, I'd buy a new one ASAP. Though I can acknowledge that other people's use-cases may be different than mine; if I weren't trying to race as competitively as possible, I might not want so much data.