Pros
Great projects to work on, for known clients, so that you can quickly boost your CV and career. All of your colleagues are somehow an expert in their domain, and everyone has a specific background. This makes it great to network and have interesting conversations. Altran does not require a lot of overtime work, unlike other consultancy firms. Salaries are ok for the sector.
Kontras
You hardly see your Altran colleagues because you work at the client's all the time. Trainings and events are after-hours. Altran has no focus, no specialisation, no real products (even though it wants to). Its name is unknown outside of France. Its values are not respected in reality, and they in fact do not care about their employees. Turn-over is really high, so you can never bond with colleagues and your manager changes very often. After a few years you usually quit because Altran can no longer pay for your career advancement and stops having added value. They know that.