Pros
there were a lot of training opportunities that helped me grow as a consultant. those opportunities allowed me to build stronger relationships with clients to get things done.
Cons
long hours are expected, with no overtime paid. if you are on a large project, that is long-term, it's harder to get promoted than via shorter projects. by promoting employees, that raises project costs if they keep you since they have to bill for you at a higher rate. unless there is no net increase in what is billable, they would roll you off because they can't absorb the financial hit. since they can't afford to lose the knowledge, they take the easy way out and don't promote. you'll see more promotions on smaller projects percentage-wise than you will for larger projects.