Pros
1) Experience: as a Project Leader, I was able to gain experience in leading teams, client interaction, and in helping others develop the "consulting skillset"; without TSL, I would not have had the opportunity to do so until several years later in my consulting career. 2) Teams: the team was remarkable. Really smart and committed folks that I am friends with to this day. 3) Leadership: the project principal (who oversees the project and provides guidance/direction) was invested in our success and committed her time to support us. 4) Projects: the project we worked on was interesting and exciting, dealing with new technology in a relatively new market. 5) Community: TSL hosts regular networking events for alumni and current volunteers to get to know each other. These events foster a sense of community that is especially valuable for those who are leaving academia for consulting - they are able to connect and learn from others who have done so.
Cons
While not necessarily a "con," your project will likely take up a significant chunk of your free time. "You get back what you put in" and the sacrifice I (and the entire team) made to contribute was well worth it in terms of the value we were able to bring to the client, as well as the skills and knowledge we gained along the way.