Utilization - being billable and profitable is managements top priority. It is the only thing that will make them drop what they are doing and actually call you. Management seems to be focused primarily on business development and utilization.
Employer name recognition and reputation - the downside of being an expensive FTE from a well known firm with high standards is that there is little-to-no leeway for mistakes.
Requirements for excellence - there isn't much room for error, the slightest hint from the client that you might be doing something less than perfect may result in a meeting with a manager and justification for not promoting you.
Advancement - Requirements for promotions are never clear and are a moving target. Everyone in the firm knows only a select few who sell business have a chance at becoming Senior Associates on the path to Partner, the rest stay at Associate-level or move on to other companies. Additionally, different teams/managers apply the promotion criteria differently. I've met a few Sr. consultants that were working at or below the consultant-level and vice versa but the consultants weren't getting promoted. Also promotions are probably given in the first year only if they underpaid you when you were hired.
Success = perception of success - If your manager thinks you aren't good enough for a promotion, regardless of how well you match the career development model, you won't get a promotion (endorsement from managers and your seniors is essential); conversely if everyone thinks you are a stellar consultant it may as well be true even if it isn't.
Individual experience may vary - the team you are a part of, and the management you fall under make up half of your experience. A good team and manager will help and support you, and provide guidance to help you improve or succeed, bad managers won't support your tasking and career work. Also the task you are placed on makes up the other half of your experience, if you are on a dead-end task your career growth will stall. Changing tasks is dependent on your career manager, so that varies as well.
Being a government contractor - The top priority is to remain billable, that is the nature of the business. And at the end of the day, we are stuck with whatever work the client tasks us with and whatever decisions the client makes, regardless of what we think or recommend.
Work-life balance - many of those who are on certain tasks can end up working crazy hours (fortunately I'm not one of them), but that is the nature of the business. Be careful of what task you end up on.
You will do more than a contractor - As you go up in level you will be required to perform more and more activities outside your task/client-work (business development, marketing, internal team tasks, assessments, interviews, etc). Networking is "encouraged", and failing to do some extracurricular activities can inhibit your career advancement or be treated as a development action on your assessment.
Income - everyone will tell you that your income is less than at other firms, especially when you are first hired. But there are many tangible (e.g. ECAP, training) and intangible benefits to working at Booz.