You have to play two roles simultaneously: be a student on your own, and have your own students. You take your own midterms and grade exams by your students during the same week. Sometimes it gets more intense. This experience may not be as relevant if you plan a research or a consultant career in a private sector. The salary / fellowship benefits will stay the same for 4-5 years of your study. Also, you are not guaranteed that your GTA package will be extended, you have to re-apply every year, and the final decision depends on your GPA being above 3.5.