I have the new Galaxy watch, received on 7th September and after 1 recorded exercise the heart rate monitor is flatlining after 10 minutes.
First run below
Second recorded walk
I am annoyed as I want to keep track of my heart rate during exercise. I also wonder if this effects the calories burned if it cannot record the heart rate correctly.
This appears to be a common theme for Samsung watches as my husbands S3 did the same, purchased Sept 2017, at the beginning of the year.
People in the USA and Canada have downloaded the update. Nothing for the UK yet.
Don't be confused by the Android Galaxy Wear app/ plug in which is also being released. I got it a few days ago. It's no great shakes - couple of extra settings you can set by phone and a preview watch face feature, also on the phone.
I had exactly the same problem, it didn't display heart rate while pretty much doing anything but sitting. After the update I got today, it is fixed, heart rate was working during my run without problems.