Pros
Exceptional training programs and on the job experiences/projects, as well as options to do completely different types of jobs as your career progresses (e.g. stay technical or move into sales, management, HR, etc). You can really diversify your experiences and keep yourself off the "plateau" that could lead to boredom elsewhere. Not a place for paper pushers- you will be challenged on many levels and can be proud of your achievements. Very international workforce.
Cons
It is a great place for a workaholic, but that becomes the expectation. As you want a life, break or family, it becomes difficult. You can certainly take vacations, but you may be working at night and on weekends, regularly, regardless of your position. Rigs don't shut down, so this is not a shock, but there are internal communication issues that could alleviate the impact of this. The structure of the company results in internal compartmentalization that you may have to regularly fight. Communication suffers. Feedback, motivation or direction from management is frequently lacking.