Pros
They have a great benefit package, starting with 2-4 weeks paid vacation/year (depending on job level), top tier insurance, paid maternity leave after 1 year, and 26 days of paid sick leave. They value long-term employment and reward employee service with raises and upward mobility options. Corporate culture is very safety-oriented and performance-driven, so a motivated person would do well there.
Cons
The oil market is constantly fluctuating, which means that your job may be in danger if the market takes a downturn. Lower-level managers don't listen to their employees or take them seriously (even long-term employees who know their job well). Interdepartmental communications can be touchy. The phrase "walking on eggshells" comes to mind. Unless you take issues to HR or upper-level management, they will go unheard. If you do so, your supervisors will retaliate by assigning you all of the worst clients (instead of just a few, which is what most people have), changing your regular schedule so that you have to work hours that you previously stated you couldn't, and creating a hostile work environment in many other ways. I was fortunate not to have to deal with most of this, but I had to keep my nose clean and watch myself at all times. Many of my coworkers quit due to the poor management in my department.