Pros
You have many opportunities working with Fortune 500 companies around the world. Because of this, building new skills is easy as long as you put forth the effort. It's also easy to build relationships (even with senior management) giving you a good network and support throughout your career.
Cons
The overtime and travel is expected for most employees. Accenture also has a high turnover rate. I've worked there eight years and according to a metric which Accenture publishes 87% of people within the company have joined AFTER me. I attribute most of this to work/life balance situations. It's simply not feasible to expect people to work the overtime and travel as much as they do. The other down side is the way the employees are slowly pushed out over time because of the meritocracy/laddering based practice. It's easy to stay with the company early in your career as an Analyst and Consultant, but as you get promoted to executive much more is expected of you to keep up with your peers. If you do not perform high enough in comparison with your peers then you are counceled out. This leads to good people leaving the company because there is only so much some people can do without impacting their family life. Bottom line is you have to ask yourself how much of your life you want to sacrifice. Usually when you are young and come in new to the company that is not an issue, but as you get married and have kids you re-assess the decision later in your career. This is why Accenture has a greater number of younger people in their workforce.