I prefer workouts like this for a couple reasons. First, anytime you end a workout faster than you started, it ups the cardiovascular benefit as well as building your lactate threshold. I cannot clearly define lactate threshold in its entirety right now, but will in a future post. Second, it breaks up the monotony. Cardio machines, as most know, can be boring. Changing speeds, intensities, etc. all help with boredom. Finally, its good for your muscles to be challenged, tricked, kept off balance.
If you simply get on a machine and repeat the same thing over and over, you lose the element of surprise on your muscles and they get accustomed to the workouts, thus settling in and being taxed less and less. New tensions, tricks, instability. All these, and others, help to make your muscles work hard in different situations.