I've recently acquired an Eight Sleep, and have been enjoying it.
But broadly speaking, it also creates a culture of intensity around sleeping and bedtime which seems ill-advised.
A few things in particular have been bothering me: an imposition of various values on the user (namely not spending time in bed without sleeping), the lack of couple-oriented features and analytics, and the requirement of having a phone near bed to control the device at all times.
More generally - by definition, the people working on products are more focused on them than users are. Users use a wide range of products in conjunction with one another.
I love reading before bed. And sometimes, I like lounging in bed in the morning. I'm not a robot pro-athlete / weirdo tech bro trying to optimize my every minute; I'm a hard-working white-collar worker who sometimes likes to relax in bed.
I want to get great sleep. I want to sleep well, and I want to develop good routines. But imposing sleep-centric values on me is generally frustrating, and candidly makes me less likely to feel good about the product and less likely to refer it to other friends.