I pre-ordered my Galaxy Watch4 and have been using it since it's release. As someone who is a cyclist, I also use a heart-rate strap connected to a bike GPS computer. I've found the heart rate monitoring on the GW4 to be problematic in two major ways: 1) It frequently drops measurement during exercise and 2) it grossly over reports elevated heart rate by 20-40 BPM. The resting heart rate recording seems okay, but given any exercise, the Watch4 is really useless. I've tried adjusting the band in tightness and location but nothing results in a useful result.
In addition, the GPS track wobbles all over the place. I know this is a Watch4 issue because I have other GPS tracking devices that show a much more stable and accurate track on the same activities.
I'm hoping these can be improved through software updates, but for now, the Watch4 is useless for exercise tracking.
Last night I contacted Samsung Support via online chat to see if they knew about the heart rate issues and could suggest a fix. The agent had me reset my watch, which resulted in losing the apps I had installed and many of the watch settings. This was despite having used the backup /restore feature in the watch to "save everything". Samsung has improved backup and settings transfer for it's phones, but the watch setting backup/restore seems to be way behind that level. It took a lot of additional work to get everything back. In particular, Samsung Pay credit cards had to be completely re-entered and authorized by my banks. What a pain!
Needless to say, the reset of my Watch4 had absolutely no effect on the problems I am experiencing with heart rate monitoring. The support person seemed clueless and was reading from a script. It doesn't seem like there is any way to get reasonable support from Samsung and the channels they have set up are a waste of everyone's time. I've been a long time Galaxy phone user and bought the watch as part of their ecosystem, but am finding Apple's quality focus and support options more and more appealing.
Yesterday I set up the Apple Watch 7 I had bought for my wife. While there are a few positive things about the Galaxy Watch 4 over the Apple Watch, the basic feeling I get is that Samsung has a lot of work to do to make a reliable and quality device out of this hardware. The HR on the Apple watch is spot on, and the GPS is way better.