1) GPS tracking is very bad and it always miss tracking some portions while cycling.
2)Heart rate tracking is worst. It will suddenly miss or stop tracking while cycling all the time.
3)sleep tracking is very very bad and inaccurate. Didn't find the watch recording the afternoon short sleeps. I some time woke up midnight 2 for washroom and it didn't record sleep from them.
Heartrate stops recording while cycling
in acccurate gps tracking.
stopped recording sleep data from 2am since I woke up for washroom
I can comment on sleep tracking. I have been using since I got the watch a few weeks ago. The sleep tracking is working flawlessly for me. I have all sensors on continuously on the watch settings. On the 23rd I took a nap, and it recorded. Last night on the 25th, I went to the bath room a couple times, and it continued to record after falling back back to sleep. I strapped my GW4 above my wrist bone, little higher than my old GW.
I've owned the Gear S2, Galaxy Watch, Galaxy Watch 3 and now the Galaxy Watch 4. Activity and fitness tracking have never been accurate on these devices. Each release I hold out hope that they fix these issues and deliver a reliable product but it never happens. There are several YouTube fitness enthusiasts that do detailed testing of the GW4 heart rate and GPS tracking. Heart rate was known to stop tracking and GPS was reported to be inaccurate. I've seen it in my own testing on the GW4 as well. If you want a reliable fitness tracker, unfortunately think you'll have to look at something other than a Samsung device to get it.
The GW4 is a good smartwatch and decent fitness tracker. Anyone looking for reliable and accurate fitness tracking should look elsewhere. I have the Apple Watch and GW4. If you have the option to switch to an Apple Watch you can't go wrong - it's the best fitness/smartwatch out there. Otherwise, look at the Garmin line for a great fitness tracker as history shows that Samsung will never get to the Garmin or Apple level of reliability.