Hack Squat apparatus?

[growlers]

At my gym there is this apparatus labelled the "Hack Squat".

http://www.bodybuilding.com/fun/exer...ame=Hack+Squat

If you click on the video it shows the guy going past parallel (which I know from this forum what you want with regular barbell squats), but then I read in some other links that tell you to only go to just parallel using this apparatus.

Thoughts on using this instead of the barbell and how far past parallel do I go?

Finally,
I want my feet pretty far back, right? i.e. straight line from feet to shoulders if you look at me from the side? Because if you put your feet forward a little it seems easier which means it is probably wrong to do it that way.... I ask because the guy in the video seems to have his feet forward just a bit than "straight line".