Pros
Very professional, has built strong level of expertise in certain areas (advertising, political polling) and the company is relatively entrepreneurial and flexible (created a separate business unit for its biggest customer P&G). Other than that it has very substantial international network so potential opportunities for international career development (should the HR function develop somewhat). Otherwise, the individuals that you come across are often pleasant, bright and motivated so that the atmosphere is a good one.
Cons
Lack of HR function in French business so career progression is a question of networking. An odd way of setting goals - strong emphasis on hitting ambitious targets for an international client but lack of reward for doing so as there are always performance issues that drag down the overall business. This leads at the very least to confusion and for those who want to perform, the clearest route to a career progression is the exit. The focus on specialisation means it is easier to get 'stuck in a rut' i.e. only work on advertising, again this does not keep you motivated.