Pros
Focus on design excellence, and client solutions is very rewarding, and allows for relatively junior staff to be important team members. Has the most dedicated staff that focuses on client satisfaction. The name really does draw out he best talent in each of the cities they have an office. They do provide the best design in most the markets they operate in.
Cons
While they pride themselves as being "one firm firm" that lacks inter-office political fighting, this is highly dependent of which office you work in. Some offices are highly political and others are not. Promotions are given out less about skill and talent, and more about how extroverted you are. Not a company to succeed in if you are an introvert, which means most of those that do the heavy lifting and the detail coordination will get left behind.