Pros
Great marketing company with driven, intelligent employees and leaders. The corporate culture is relaxed and respects work-life balance at all levels. I can't say enough about the people. Amex employees are very social, involved and generally very nice people to work with. The company has a great reputation as a customer-focused marketing company. Innovation and creativity are valued and rewarded. Although the economy has had an effect on job mobility within the company, there is a strong culture of trying many roles within the company and this mobility is a key selling point for many employees.
Cons
Decision-by-consensus often means that projects move slowly. Upward mobility at the lower levels can be hindered by lack of MBA. Lately, job mobility has been stagnant, which has caused some employee unrest (this should free up soon.) Morale and corporate culture can vary dramatically by role, but even the "bad" groups are pretty good.