The pseudopotential panacea

Webster's dictionary defines panacea as a “remedy for all ills or difficulties; a cure-all.” A pseudopotential is an approximation to the real potential an electron feels in a solid. In what sense can it be called a cure-all? What are the ills it cures, the difficulties it overcomes or the problems it solves? And how does it help solve problems? Our object here will be to supply some answers to these questions and to describe the growing influence of theories involving pseudopotentials on solid state or condensed matter physics.