Pros
Great colleagues. Good working environment with lots of trust and solidarity. You will probably get to travel quite a bit, visiting all sorts of rather exotic places were oil is produced. You will get to work with people from a large number of countries, people which you would otherwise never meet.
Cons
Very little formal training, most people join, is put on a project and simply learn the job the hard way. Few internal rules about how to progress with any project. While this gives people on a lower level a slight chance to improving or adapting things it also results in a very chaotic working environment where no one is clearly in charge. The basic problem of the company is that they agree to almost any specification the customers give them. While this in theory sounds like service it prevents any movement towards having real products. Instead the company simply builds subsea infrastructure, one one-off after the other. At the engineering level this prevents development of standards and gives people the feeling they are not good enough for their own jobs.