Pros
Nice office locations, some really smart coworkers, better benefits, feeling of "We Shape the World" which is soon destroyed when you stop being an "Arupian" and go see the real world.
Cons
Only way to get promoted is to use big words in front of your bosses. Very little career advancement for silent and smart hard-working people. All upper management consists of "brought in" British people. They selectively give leadership roles only to imported British folks. Each office has a big system in place to bring 8-10 British people over for a year or two on Long Term Assignments (LTA) and then keep them in America forever so that they can be the next bosses. 90% of the projects (In Buildings department) are new office buildings or Tenant improvement (TI) in existing buildings, so architect firms like Gensler are the ultimate client who dictate everything . Hence no job satisfaction if you are a proud engineer. The rest 10% of the projects (healthcare, datacenters etc) are done by the select few people who don't want to share their skills and experience with new people. Entry and mid-level engineers are paid atleast 20% less than the industry standard. Arup hires lots of underpaid graduate engineers and get bulk of work done by them. This helps them pay fat salaries and business class travel expenses for the "British rulers". Company works on a slim profit margin thanks to extensive wasteful overheads. They take pride in the fact that they are not publicly traded, but in reality that is their biggest weakness - there are no checks on these wasteful spendings. Only diversity exists at junior staff level. At higher up ranks, Arup is a white, male and mostly British party. There are big meetings and regular emails about "Diversity and Inclusion" efforts and only people talking in them are 'concerned white people'.