Like others, I agree that it depends on what you want to study. I, too, have seen lots of Nurse Practitioners unable to find good jobs. However, the children's hospital I work for has a 40% vacancy rate in its Clinical Nurse Specialist positions. We are desperate for Master's prepared peds nurses who want a role that emphasizes staff development, bedside teaching/consultation to the staff nurses, policy development, etc. Most PNP's are not prepared for those types of roles, even if they are willing to give them a try.
Similarly, the world needs good managers and administrators. Someone has to run the hospitals and other health care agencies.
Finally, the world needs nurses with graduate degrees to teach in schools of nursing. The pay is terrible (unless you get a PhD, and even then, it takes a while to climb the ladder high enough to get a good deal), but with a little pressure from the nursing shortage, it might improve.
Finally ... educating yourself should not be about just finding a job. The job market changes from year to year and it's a mistake to choose a career path just because it's "hot" at the moment. You may find yourself 10 years from now prepared for a job you hate. I also say, "Go where your heart is."