That's bogus man,
I weigh 116 kg, that's over 250lbs, and warm-up with pullups. After two or three sets, I use a belt with dumbells attached up to 70lbs (32kg). You cann't compare pullups with lat-pulleys in any way. The excercise and the position differ two much.
With pull-ups, you will try to get your upper-body horizontal and do a kind of high-row. With the latpulley, you start pulling with your lower back. You lower back can lift an amazing amount of weight, so cheating with the pulley is absolutely useless.
Cheating with pull-ups doesn't hurt you so much, you still using your back to lift the weight, the angle is slightly changed, but it still makes it a good excercise. And adding weight on a belt makes cheating by with "airwalking"(don't no how to describe it otherwise) almost impossible.
About dips, everyone knows the excersise, almost nobody performs it. Usually it's a combined rack for legraising and dipping. 9 out of time 10 times I see people do legraises.
There's also another machines where you can perform assisted dips, but that's the biggest piece of crap I've ever seen. Everybody should be able to lift their own weight without assistence. It's crucial for building the right amount of mass without getting the buffed look. I would recommend it to al girls, they usually tend to have big legs through running, cycling, and stepping, but skinny-ass upper body.