Pros
The front line people of the organization and the project leads are excellent professionals, smart and fun to work with. The sector is fascinating, too bad it makes no money. You get to work on cool projects in interesting locations, and it is a great mix of public and public, local and global. US, Swedish and Australian teams are motivated and talented. I cannot complain about the opportunities accorded to me.
Cons
This company underwent nothing but mergers, spin offs, rebrandings and restructurings during my 8 years there. Senior management in Paris was always meddling and overbearing, yet oblivious to what was happening around them. Many of them would be fired immediately for incompetence in a US company (in France they just keep on occupying space until retirement). Generally they were more concerned about each one's own skin than their team or the company objectives. CEOs (Richard, du Peloux, Janaillac, Gaillot) were always opportunistic, clearing viewing the company as nothing more than a stepping stone. It's reflected in the increasingly zombie-like company culture, like a forgotten middle-child. The most often used adjective people used to describe Paris headquarters was "morose". The company had a strong portfolio of projects when I joined, and I watched the company lose contract after contract until the time I left 8 years later. There's a whiff of corruption all around, but not easy to put one's finger on it.