Yes. I do think they will help with squat strength, as long as you don't overcook it. However, the best thing to do to develop squat strength is to squat.
That said, I do a couple widow maker sets of leg presses after I squat. I have access to a hack sled, but they get to be wicked on my knees. If you're back squatting more than once a week, I wouldn't add them in any more than once a week. Either hacks or presses are a good supplementary exercise. Maybe on one day you could go heavy on the back squat and do a high rep chaser with the leg press or hack. On another day you could front squat without a chaser. And on a third day back squat with maybe 80% of the weight you used on the first day and again no chaser.
Bogdan Petia Sarac - Must keel moose and squirrel
Cancer Survivor - 7/21/10
Benchmark 5K time: 27:45 (3/5/11)
It's not the weight we move, but the people we move that matters. -- Bearded Beast of Duloc (12/31/10)