This exercise targets your upper lats and is a great exercise for shaping and toning. The lat machine provides for a smooth and fluid motion. Thus, beginners especially like it.
If your goal is to put on mass, you should do back exercises that involve the use of barbells and dumbbells. The lat machine will not help you much if you want to pack slabs of muscle onto your back.
Another thing worth mentioning is that your posture is important when executing this exercise. Do not lean back too much and don't attempt to pull the weight by utilizing the momentum of jerking motions. Always do this exercise with a smooth continuous motion.