Pros
Union Pacific is a strong stable company that will only continue to see an increase in business fueled by the increasing fuel costs to transport large commodities. With that said, you don't have to worry about the company going under. Although, you sacrifice some things in your personal life, you do have the freedom to complete your tasks, and monitor your responsibillities without being tied to a desk the entire day. Your average work day is about 12 hours give or take, but those 12 hours are not all spent glued to your desk. Also, there is opportunity for advancement, and the jobs pay well.
Cons
As with all large companies, politics can be a downside, where advancement is not always based on merit or achievement. Also, if you do not have an understanding spouse the long hours and hollidays have the potential to create issues at home. You will work long hours, nights, weekends, and holidays and could potentially have work days turn into a 30 hour venture. The downsides to this job, are not specific to this company and are shared by all companies which operate 24 hours a day 365 days a year.