Pros
Shell offers very competitive pay and benefits, professional development opportunities and support through life events. It's a huge global company and they've encountered just about / prepared for every kind of situation an employee may experience. Misbehavior is not tolerated.
Cons
Ultimately, the company's roots are in The Netherlands which is a very (characteristically, not politically) conservative culture. Shell is very slow to adapt to evolving cultural norms, preferring to watch and wait before making operational changes. As an example, Shell consistently ranks in the Top Five of supermajors but never #1 because it is too ponderous. Another example is the pension plan, which was growing at rates of 3-5% a year. While this is a conservative approach to ensure stability and consistency in future returns, it does not keep up with cost of living increases or inflation. This perspective is also reflected in work processes. It can be stifling to creative, enterpreneurial and / or ambitious personality types.