Pros
Work life balance is good if you're in Paris. It pays quite well. Young people (because there some turnover), good working envirnoment.
Cons
They send me directly to the client, just the day I arrived. If you are on a mission, don't count on their support. You're a bit alone. No follow up on your career: what will I do next ? Nobody will be able to tell you. You keep you job for >3 years as everywhere in France in the engineering sector. Also you will quickly become a specialist (eg of the automatic metro technoology, of the electrification of a railway...) and this will stick on you forever ! Keep in mind that I worked there before the merger with Inexia. Since then the company has doubled of size and changed adress, senior management etc...