Pros: i get to teach!
Cons: i have to teach!
I enjoyed my time as a T.A. I was surprised it was cut short. My lab sections were about 4 hours long. I arrive, typically, a half an hour early. I set up all the equipment. I review the lecture material, and set up the overhead for the presentation. When the lab section begins, I collect homework, take roll, and answer students' questions as they arrive.
I learned to be very organized with my time. My supervisor gives great advice, which I followed to a "T". I liked all of my fellow TAs--everyone contributes equally to the creation of the week's quizzes.
The hardest part of the job is at the end of the day when you are tired of standing. Students are bustling around trying to finish up, and you must be aware of lab safety at all times. the most enjoyable time is quiz time. It's the only time the lab is completely quiet.