Yes, it is amazing. They say Heart Rate Variability is pretty good indicator of stress. My HRV graph for last 6 months clearly shows when I made decision to change job and when I gave 2 weeks notice.
My heart nerves got jacked up a couple years ago, and I had to get a pacemaker. It's presumably collecting a ton of cool data that it BLE's to the manufacturer and my cardiologist, but I don't have access to it.
I used the swagger interface a few months ago to download my resting heart rate over a three-year period, and it was interesting.