Others have touched on some of these.
1) Should be able to pull in actual sleep data from Sleep++ or Resmed.
2) On the sleep checker - needs an option where the input format lets you enter numbers versus/in addition to scrolling.
3) This may have been by design, but it's behoove the research to collect voluntary info on other diagnosed conditions and/or prescribed medications that may influence sleep/alertness.
4) Curious survey asks about diagnosed sleep apnea but no follow-up on AHI or other metric to determine degree of severity...or how long ago. None of which can be provided to the HealthKit for collection like weight and blood pressure. Or for that matter they should collect info on what machines are being used for integration/partner development.
5) No questions about sleeping environment such as temperature - I haven't fully explored the app but haven't seen anything yet. Would be interesting if it pulled in data from Nest/Eve thermostat.
6) Not sure what dietary data they may be pulling in from HealthKit but, for example, while I am fairly rigorous about using MyFitnessPal I rarely track coffee consumption. In my experience most dietary apps also poorly collect data on first meal and last meal.