Doesn’t do what it says on the tin.
Unreliable, and will unintentionally rate unplayed songs
To fix the damage caused, I had to remove this app, synch my iPhone to my library, restart the iPhone, fix the ratings that this app broke (redundantly stored as text “***” in songs’ Comment tag), then re-synch.
If you actually care about keeping song ratings, my recommendation is to proceed with caution with this app. It is buggy/unstable at best, or worse… poorly designed. Either way, it can’t be trusted.