Pros
The firm takes care of its employees. Many consulting companies only hire somebody for a specific contract and when that contract ends, the person is left looking for another job. Booz Allen hires you for you and not for a particular contract. Therefore, if one contract ends, they actively seek out another contract that is of interest to you. The firm also has excellent tuition reimbursement benefits and 401k contributions (whether or not you participate). The firm also has a lot of community outreach activities to help improve the local community. Booz Allen is one big family who looks after each other.
Cons
Like most other large consulting firms, it may be difficult to get face-to-face time with senior leadership. The firm is reaching out more and conducting more brown-bag discussions to let employees know what is going on within the firm. Many of the employees spend most of their time on-site with the client. This makes attending firm functions difficult, especially lectures/presentations given back at the headquarters. From some sites, it might take half a day to go to the event, attend the event, and then get back to the client site. You would normally have to make up those hours or take leave.