Pros
The pay is great, especially for the physical demand of most days of work. This is regional, obviously, but I enjoyed working with mostly every person I came in to contact with, which always makes your job better. Guys complain about the health insurance premiums, which really aren't too bad, especially since it is the same just for you or if you have a wife and 3 kids, but even then co-pays and costs are very good.
Cons
Work-life balance is difficult. Job security is poor, arguably even nonexistent depending on the local railroad economy (i.e. coal, fracking). Relationship between union and management is, at best, strained. You can get "fired" for any number of things, which is somewhat understandable, but if an incident occurs they have the rules written in a way that they can almost always lay blame on you.