Pros
Very professional, friendly and proactive agency. As part of my initial interview I had to give a 10-20 minute tutorial on a topic of my choice. This was casual, but by no means just a formality, as the Profs insist on a high standard for their tutors. Since then they have provided me with a consistent stream of tutoring opportunities from undergraduate through post-graduate. (For me this is a real bonus as I prefer the variety.) Finally, they deal directly with the clients regarding payment and ensure everything is sorted quickly with minimum fuss.
Cons
I can't honestly think of any real negatives to working for the Profs. Everything I would have expected a tuition agency to do they have done in a prompt, efficient and friendly manner.