You cannot cheat when you're tired. It is just like having a personal trainer without the steep cost. I like that I can track my HR during the workout and compare it to others to see if I'm pushing hard enough.
I like that it's not only a workout for muscle toning, but it also focuses on teaching you how to find your personal cardio level. I also really like that even though it is a group class each person is given coaching on an individual level.