Now that I've been playing Pokemon Sleep for a while I have some game design thoughts about it:
I think it's a bit upsetting that the way to actually move forward in the game is not tied only to having a good sleep session, but to opening the app at least 3 times during the day to feed your Snorlax.
( The amount and types of Pokemon that show up when you sleep is linked to your Snorlax power, and your Snorlax power increases by feeding it berries your Pokemon team finds throughout the day and by feeding it Breakfast, Lunch and Dinner. )
The amount of time the app requires you to spend on it every time you open it is very short, probably less than a minute, but being required to get my phone in 3 different slots during my day is very disruptive. It's a sleep app - I'd feel happier about it if I only thought about it before bed, and right after I wake up.
I also think progress being reset every Monday and you always having the best progress on the weekend and slowest progress at the beginning of the week is sad, because I wanted to have something cool to look forward to during work days. I wish we could set up which day we want to reset so I'd have the coolest Pokemon on slow Mondays and Tuesdays >w>
For now I'm sticking with it because it's at least encouraging me to go to bed at a consistent time, and I really really enjoy the Pokemon sleeping animations. But I really wish the "mobile experience" wouldn't taint it so much - I don't think I'd even have minded the paid Sleep Pass so much if the game was more focused on sleep. alas...