Conventional wisdom of course says that overachievers always help an employer, but I wonder if this is really true. I'm not talking about good solid competent employees, even ones who occasionally take on a special project from time to time. I'm talking about the Super Employee, who is constantly overachieving to the point that it disspirits the other employees. Does this kind of person, this Super Achiever, actually cause morale problems among the overall people in the department by creating unrealistic standards that others are then expected to live up to?

Do such employees, always help, usually help, sometimes hurt, or always hurt, overall preformance of a department or company?