What Mel posted is what I was familiar with as well. Here is the barbell version of the hack squat http://jva.ontariostrongman.ca/HACK.htm
The freemotion machine that Meg posted is similar to a power squat machine.(seen used in this video at 2:45 http://www.youtube.com/watch?v=-UV7h9NC0Ag
) I don't know if the Weider is trying to replicate one of these or if it is supposed to be used facing away like a real hack squat machine. Either way, I think the foot pad needs to be larger and angled in order to allow you to maintain proper positioning.
However, I could be wrong. If your machine allows you to squat with proper form, chest up, weight on heels, sit back and down with the hips, etc, it would be a good option. If, however, you cannot maintain proper form or if like Mel said, doesn't feel right choose other options.