Pros
High profile projects, a diverse range of work and people, relaxed atmosphere. Everyone up to high-level directors stay involved in the design process, and there are no 'stupid question's in Arup. You work in small teams on your specific projects, and so can take real ownership of your work... but you can ask the whole firm a question if you get stuck - and someone will always know the right answer. We have a strong set of values we continue to stick by, and are employee-earned so can control our own work.
Cons
Not the best salaries in the industry, but makes up for it by providing an enjoyable days work most days. You can easily get sucked into the culture of working late, but people do it out of choice because they want to make their work better - no-one has this forced upon them.