Had it year ago, along with Whoop. Withings Sleep consistently reported less time in REM & SWS phase than Whoop. But regardless of actual numbers, both are great tools to learn how you respond to different things related to sleep (drinking, reading before sleep, consistent time going to bed etc).
Anyway, after adjusting my habits (~4 months) to improve overall sleep quality, got rid both of them – monitoring fact itself and obsessing over numbers started getting to nerves. Still, definitely helped me.