I've had mine since March and it's been pretty great so far. I have questioned 'jail breaking' it to use gadgetbridge instead of zepp, but I haven't been bothered to as of yet.
I have two criteria for this kind of thing. The sleep tracking has to be automatic, not requiring turning it on at night, and there has to be an API or it has to sync to Apple Health. Do you know if it has these?
Sleep tracking does start automatically. While I cannot find an API directly from Amazfit and Gadgetbridge is Android specific, it does look like you should be able to go from their Zepp app -> Google Fit -> Apple Health. Do you have any experience with Google Fit on iOS?