for cardio anyway since it really gets you winded and sweaty; i am assuming you are talking about squats w/ a barbell (rather than the seated or standing machines) since it works the upperbody in that you have to keep the weight balanced;

however, deadlifts are a lower back strain waiting to happen for me (guess that's form but i can't seem to get it right); anyone have suggestions about an alternitive for deadlifts that are safer? how about a "deadlift" using two dumbells so i don't get bent over?