Pros
Great experience, especially if just starting out in oil and gas industry. Lots of industry-leading equipment/tech/etc.
Cons
If you can't handle long hours, harsh conditions (at times), and being away from home for long periods of time, this job isn't for you. My experience at Halliburton was also that many people feel like they're just a number in that management will make frequent (and often sweeping) changes to processes, workflows, engineering schedules, etc. Lots of bureaucratic hoops to jump through in order to advance through the three levels of Field Engineer before you can "break out" and really make good money.