Pros
Booz Allen is the ideal place if your primary requirements are work-life balance and a pleasant work environment. The work hours are very flexible and the pay and benefits are great compared to the amount of effort you are required to put into the job. The work environment is fantastic if you are lucky enough to be at a large booz allen site. Lots of friendly people and a variety of office events, parties, happy hours, pot-lucks, and other networking events. The Booz Allen name is still a prestiguous brand.
Cons
The main problem with Booz Allen is the work itself. The firm has transitioned from being an elite, high-end consulting firm to simply being another government contractor. The majority of the work is basically "low-end" government support/staff augmentation work on long-term government projects. I personally came to Booz Allen directly after finishing my graduate studies in engineering with high hopes of participating in challenging consulting engagements for a variety of clients. However, my actual experience at the firm was significantly different from this initial vision. For four years I was basically stuck on the same government program just updating the same government documents over and over again. We were called "systems engineers" and were supposed to be real technical and business advisors to the government, but in reality our role was less of an advisor and more government staff augmentation. Again I think its a great company if you aren't really looking to work that hard and grow professionally. Its great for ex-military types that are looking for a second career right before retirement or for anybody whose main priorities are things outside work and are not really interested in building a career. However, if you are somebody that really wants to grow and stretch themselves through challenging projects then you will be very bored and dissatisfied at Booz Allen as I was.