Pros
I had been in academic research for a while, and TSL was my first real exposure to a business-oriented project. Working on a TSL project, while simultaneously holding a full time job in academia, gave me a small taste of the pace and commitment it takes to be in client business. I recommend this to science PhD /MPH students, post docs etc who are considering to potentially go into consulting or another client business. My team was extremely committed to producing quality work and pleasing the client. It was remarkable to see how each person contributed to deliverables using a skill set that no one else on the team had. They put together the team very well. On my team, everybody was a volunteer, but we got free meals at team / TSL get-togethers a few times during the project. I learned a lot from my team mates who already had some TSL project experiences. Also, thoroughly enjoyed the sense of accomplishment that my team shared after the 12 weeks or so of hard work at the end of the project period.
Kontras
Just like working for a real consulting company or investment bank that I ended up doing after the TLS project, working for a client was a lot of pressure that I had never seen in academia primarily to meet deadlines and produce quality deliverables. But the whole point of doing this was for me to see if I could enjoy "fighting" to please a client.