Pros
Culture is highly collegial, and teams really do pull together from many disciplines to solve hard problems. I've think we work on more interesting assignments that I've heard of at other firms. I really respect my colleagues for their technical ability. Booz Allen lives its core values. I feel there are a lot of people here like me that work hard and play hard. Hours can sometimes be long, but when we blow off steam, we blow it off. The extracurricular sports leagues are amazing...flag football league has 19 teams, 3-on-3 basketball has former college players, running club does marathons together, etc. Firm has very strong prospects for growth.
Cons
Promotion process can be very hard to get into more senior management. Salary tends to be a little lower than at smaller firms. Management is OK, but not a Booz Allen strong suit. Firm is very flexible. If you can't handle ambiguity, you aren't going to make it here.