Pros
Some very skilled and talented people Very human (understand emotional in the good way) and skilled top management Fast growing, fast moving environment Solid & real opportunities and room for professional growth for those who are willing to push smartly above their job titles initial attributions As fas as I'm concerned the diversity and level of projects (from International creative campaigns to AR, VR, UX, Data, CRM, Apps, E-Commerce, Loyalty programs etc.) is a very good thing as you could be continuously lead to learn and evolve out of your comfort zone. Of course it depends of your will to do so and I understand that it's not necessarily something everyone would look for.
Cons
Everything isn't yet processed in the optimal way but huge improvements have been and keep being made. The other downside of working in such a fast-paced environment is that projects are sometimes coming in faster than the ressources hired to tackle them can actually start working here, leading to occasional overtime but nothing unusual compared to a parisian agency I'd say. Like in any relationship, it's also up to you to set the boundaries along the way and there are many parents (and not only) who have done this without any specific issue or professional discrimination for instance. You need to be comfortable with a specific industry if you want to work on top-level subjects for the main client as the others don't necessarily have the ressources to invest as heavily to address cutting edge topics.