Pros
Very cool projects that look great on your resume for when you leave and decide to work somewhere else.
Cons
Arup has a cult mentality to them that is often pervasive in large companies. The people are truly the best and the brightest, but with that you also get the ugly side of people such as arrogance and snarkiness, something I experienced face to face often. Maybe it's a cultural shock for me since I'm not from the United States. The pay is also very low, but Arup justifies that by saying you get to work on cool projects. Work life balance is horrendous. I find it amusing that the only people in high rank positions who had families were mostly men, while many of the hardworking, high level female engineers were single and childless.