I do all kinds of workouts.
I do straight set training followed by cardio; I do one day weights, one day cardio which is NOT just a machine but sometimes my bike, sometimes sprints outside, sometimes running stairs; I do sets where I do 1 set of 50 reps, but one of my favorite kind of workout, especially when I'm short on time, are these kind, the ones that incorporate muscle building and cardio in the same short time span. This one is for those days when all the gym is busy, because all you need are some hand weights and a bench or workout-step to step up on; OR you don't need a step at all. You can do the whole thing right on the floor but the step adds intensity and more muscle burn!
This is one example of the kind of circuit I love putting together. I like to call it the SmashFit Bench-tensity Workout!