Hi, abnicu. I was one of the first people to get an MSN in perinatal nursing 30 years ago and worked as a NICU CNS for several years. (In recent years, I have moved on to work on hospital-wide projects in the field of Nursing Professional Development rather than being based in the NICU.) I've worked in several different hospitals in different areas of the country over the years.
Most of my NICU CNS jobs involved a lot of staff development, coordinating orientation and providing the existing staff with on-going education. They also involved the development of policies related to NICU care, the evaluation of nursing care, and the implementation of projects involving changes in practice. In some jobs, I ran parents' groups, got involved in discharge planning/teaching, and a little research.
In short, my jobs have been a hodge-podge of "doing whatever work needs to be done." In my experience, the CNS is the "go to" person for all those functions that staff nurses don't have time for and that don't fall neatly into another person's job description. That seems particularly true of a new CNS. I found that as I got older and more experienced, I was more able to shape my role a little better -- and "pick and chose" my priorities a little more. Not totally of course: it's always important to be flexible enough to pick up a few "other duties as assigned" now and then.
As for salary ... that varies from region to region. Obviously, nurses in the big cities with high costs of living earn more than those in areas with lower costs of living. In general, CNS's usually earn about the same as a mid-level manager -- more than staff nurses, but not as much as upper-level administration.