Pros
Flexibility to balance work and life, absolutely feel no guilt in taking time off for work for example. Friend who is pregnant (and going on maternity) was recently promoted to VP despite her condition -- she was the right person for the job. They will allow her to work from home for the first year. Focus on professional and personal development -- my leader spends significant time with me to review my 360-degree reviews, create development plan, and put real resources and time behind my development (even at specific cost to the company). Great decision to join American Express in London.
Kontras
Employees have the ability to change jobs every 12-18 months, which is great. But the downside is that this creates a void of institutional knowledge. A lot of time is spent re-inventing the wheel and/or tracking down the people that originally worked on a project. American Express is also a very heavily matrixed organization, so it takes a lot of patience and influential abilities to get things done. You are often goaled against objectives over which you do not have direct control. This has certainly been an area of frustration, particularly if your goals are not aligned with those you are trying to work through.