Working at Arup was a great experience, surrounded by smart, motivated, and mission-driven peers.
Cons
This may have since improved, but at least previously, the America's region felt rather second-class compared to UK. Most/all senior leadership, even in the US, was British.
Great company with lots of good benefits, interesting large scale projects, and a fantastic team of people to work with.
Cons
Be prepared to work long hours, overnights and weekends at times. At the end of the day, it is a consulting firm so the clients needs will always come first over employee health and wellbeing.