My wife is a big fan, drawn in by the songs she recognizes and the promise of exercise. But ever since we visited Japan and tried the rhythm games in the arcades there we've both felt Just Dance to be a bit lacking -- the tracking isn't very sensitive and has a huge tolerance for accepting wrong/mistimed moves
This is referencing Philip Wadler's 1989 paper "Theorems for Free", which is fairly well known in the Haskell community: https://home.ttic.edu/~dreyer/course/papers/wadler.pdf