Pros
Fantastic learning opportunity, great travel and benefits and some bright people to work with (emphasis on the some). THey give some good pay and recognition and their final salary pension scheme is excellent. You'll also get exposure to a wide variety of different cultures and overall I preferred the style to that of an Exxon or a BP. You don't need to do much to be a star...
Cons
People in jobs their totally unsuited towards, a complete lack of looking outside the company and their HR is poor to say the least. I worked with some great people at Shell but sadly there are quite a few who really were totally unsuited to the work they were doing. They had no background in it, no experience and no great desire to learn more. They saw their roles as a stepping stone to something else.