Pros
You'll have exposure to high profile projects, and have the opportunity to learn from extremely driven and ambitious management. Managers run a tight ship, which produces high quality work but can be time-consuming. Transfer opportunities are excellent, and it's possible to change engineering disciplines within the company. The office facilities and home office stipend are great.
Cons
The people who excel at Langan are very competitive and are those who center their social life around the company. Networking and participation in industry organizations in your spare time is emphasized. For some people this is achievable, but for most, this can lead to burnout. Working early mornings, late nights and weekends is normalized, and often compulsory. Langan are working on diversity initiatives, but recruitment from a select few colleges (e.g. Cornell, Columbia) hinders the diversity of the applicant pool. The courtesy two-week notice resignation period was not honored, which was disappointing.