Pros: Great stability and control. Less chance for injury. Well engineered and constructed.
Cons: Doesn't hold enough weight for those that like to kill themselves in the gym.
It give much better stability during squatting so that the lower back is not in a dangerous position. That is, it allows you to hold the back in a true vertical position. Additionally you can vary the leg position to change the effects of the exercise. This is much better than my smith machine for doing legs. Much better on the knees and back. And to top it all off, 3 time Mr Olympia Frank Zane himself has been using this machine for years.