The app has one main job — it should sync reliably, in the background, with my band. While I have it set to sync every hour, iIt doesn’t. This means that I have to open the app and manually sync, which involves trying to tap a very tiny target that is next to the home button and then waiting for often several minutes. This makes the app essentially useless for a quick glance at my recent history. I have tried several deletes and reinstalls, after which syncing works nicely for a day or two and then stops again.
Additionally, either because of limits in HealthKit or, more likely, Microsoft’s desire to own my health data, the app will pull step data from HealthKit but will not insert steps, heart rate, UV, or any other data back into HealthKit.