Ok. I have tested it a few nights now & it performs pretty great.
One criticism though, it won't track your sleep
beyond your schedule. Last night it noticed that I struggled to get to sleep, which was true. And then I notice the graphic is kinda fall short to the right (yellow rectangle). It doesn't fill the whole area.
Last night I slept way beyond my alarm (5.30 AM), woke up at 7.40 AM. The watch didn't include this extra data even though it knows when you
actually wake up (that's why there is a blank area).
View attachment 2065356
So I checked the day before - I woke up at 4.30 AM that night, 1 hour before my alarm - and the graphic fills the whole area.
View attachment 2065357
So any data beyond your sleep schedule will not be included & that means your 'Time Asleep' (including REM, Core, Deep) - in red circle in 1st photo - will be incorrect
unlike the previous iOS which always counted it & was correct.
I work from home

so it's super easy to adjust wake up alarm to compensate for this. I suspect many people wouldn't be able to. Hope Apple fix this.