Pros
Smart, talented people, great pay, lots of high-profile assignments. Sure, it's Federal Government consulting- and if you've never worked for the Government then that takes some getting used to. There is a ton of opportunity, but you have to really be an entrepreneur and make things happen for yourself. The soft skills you learn here will serve you well anywhere else you go. I've worked for many different companies, large and small, public and private, and I can say that I like Booz Allen the best.
Cons
The assessment process is a giant pain in the arse, but I've been on the giving and receiving end and I believe it's the best process out there. Your Booz Allen experience is very, very team dependent. If you end up with an inexperienced manager, your life is going to suck, and badly. The culture is very hierarchical, and there's not a lot of communication between teams- although there is a subculture of people who are trying to change that.