Pros
A lot of bright and talented individuals. A lot of complex and challenging projects to work on and they utilize the latest in design software and command a presence in the industry. They are respected in the civil engineering community. They've been around for over 100 years so they must be doing something right.
Cons
Moving up in the company can be tough depending on your own situation, it varies from office to office. Also they would rather "steal" top talent from another company instead of growing/promoting their loyal employees. A lot of "brown-nosing" individuals careers are accelerated even though the natural talent may not be there. Professional development was discussed but hardly ever supported. The employee review process was given much more importance but if your supervisor is unwilling (or doesn't care) to see you grow and succeed.....good luck. Also, the "legacy" (30+ years) employees were some of the most bitter individuals there. Some high level individuals were some of the most conceded people I've ever met, thinking they were "important" in their little HNTB bubble