Pros
Good place to start a career due to variety of assignments and travel opportunities. The other great benefit is that the firm is without a doubt the best at what it does (a relative distinction, however), sells like nobody else in the business (a double edged sword) and is a truly global organization. Exposure to other countries, cultures, and work forces is a great experience.
Cons
Too much travel. Sales team over promises, delivery team under delivers. As a member of the Outsourcing line of business there was the dual downside of being a facilitator of the movement of good paying jobs located in America to overseas locations (Eastern Europe, India, China, Philippines) and having to plan and implement "Knowledge Transfer" activities (i.e. please train your replacement). Unless you're in the Thomas Friedman camp on world economics it's depressing work. The other difficulty I had was as a mid-level manager, I did not have a great deal of autonomy or authority in the projects I was assigned.