i completed the 5 days, the biggest problem i got while playing is that the switch minigame doesn't work most of the time and when poppy and sammy's minigame happen at the same time cause you don't have enough time for both.
it does keep you on your toes while doing stuff but i found that you can just keep the left door closed and recover all your sanity without worrying but i don't know if sanity is meant to go down from nothing.
i say that its fun but it does have a difficulty to it which is not bad at all!, i had fun playing it and i can't wait for more!.
if i was to ask for any change... i don't think i would (apart from bug fixes), i think its good.