Pros
The company has great benefits. Management does a pretty good job of making sure you get your allotted time off. That is not the case at many competitors. The training you will receive is top-notch. Your job is typically pretty secure since the company is so large and they do their best to not have to lay off workers. Sometimes it is unavoidable, however. Should you stay with the company there are many opportunities to advance and move up. Engineers get their own company vehicle, laptop, and smart phone.
Cons
Too much bureaucracy and micro-managing. Top-level managers in Houston will be making work decisions for you, which is usually not a good thing. The amount of paperwork required for the position can become borderline ridiculous. The company is so large that you are just another employee number to them. You can make more money elsewhere. This job is very demanding. Hard labor, long hours, long drives, away from home for days or weeks at a time, irregular schedule, and working with hazardous equipment (explosives, radiation, high pressure). The oil and gas market is very volatile, there are booms when everything is good, and busts when you will probably be looking for a job.