AIUI, the main limitation with &Cell<T> is (1) no provision for concurrency, obviously - though the various Atomic* types work similarly via interior mutability; and (2) data has to be read, written or modified as a single operation - any provision for enabling subobject access or the like is quite ad hoc, and has to be implemented for the specific type you're working with. GhostCell (and QCell, LCell etc.) generalizes this by tracking the use of shared references at compile time, such that writes will not overlap with each other or with reads, without enforcing a "get/set in a single step" workflow.