Pros
Excellent growth and development for younger staff. Opportunities are available for those who are willing to work hard and distinguish themselves. Large companies mean that there is always an opportunity somewhere. Excellent compensation and company is supportive of work life balance. Balance is key, sometimes business needs dictate that you need to work extra, sometimes life situations such as family emergencies, child births and health issues lead to situations where employees need support. I have always found Shell very supportive during challenging life situations.
Cons
Nothing major from me here -- cons are very dependent on personality and fit within Shell's strong corporate culture. If you are not proactive about establishing a network, it can be difficult to get things done. Networking is very important in this large company as it is hard to stand out with the large amount of intelligent individuals in Shell.