Pros
It's a stable, profitable company with tremendous career potential, good pay, and great benefits. The retirement plan is excellent (Railroad Retirement is better funded and more secure than Social Security, and the 401K plan has many good options all of which receive 30% immediate employer matching). They are also the safest railroad to work at, with all departments maintaining a safety focus at all times.
Cons
For some employees, including unionized clerical workers like me, there remains a private life outside of work. However, for NS and most railroads, the general attitude is to have as few employees as possible. They will overload you with work and expect you to get it all done even if you stay late consistently and/or work weekends. The company also has not yet adopted a progressive, team-based model of business; it retains a very heirarchical, structured, individualistic approach to work.