Vantaggi
Booz Allen Hamilton does a good job of providing their employees with some tools to help them succeed in client engagements; a faster computer, networking connections to more experienced professionals, and even while working for government, insulates the employees somewhat from unnecessary regulation and trainings: You have more flexible working hours than your government colleagues.
Svantaggi
Booz Allen Hamilton is famously a "sink or swim" organization. Their business model is billable hours, so its no surprise that they try to put you in front of client as soon as possible, even if that means you are undertrained, or alone. It also means that you oftentimes don't get to choose the clients or work you want, as your managers will have the role of keeping "billets" filled, and your interests don't make the business money. The facilities in which you work are often run-down government buildings with poor IT infrastructure, and clients who are themselves government bureaucrats often espouse an obstinate opinion on how things should be done. Creativity and ambition are consequently not rewarded half as much as conformity and obedience.