The reason I'm asking, is that I work out at several different gyms, and the cable pulldown machines are not set up the same. One gym I'll do my sets at 100 pounds, for example, then the other gym, I'll do my sets at 200 pounds. Am I magically twice as strong at the other gym? No, the machines are set up differently. My trainer didn't realize this, until I pointed it out to him, so I think a lot of people might not realize this. If the bar is moving down one inch, for every inch that the weights are moving up, it's one to one, and the weight you have set, is the weight that your lifting plus some additional force due to the friction of the pulleys, etc.
Another example: Hammer Strength Leg press machine. The sled is at a 45 degree angle. Load up 900 pounds of plates, and are you really pushing 900 pounds of force? No. It's more like 636. But if you asked people at the gym, I'm sure they'd all say it's 900 pounds.
-Tinytoad