I moved to leg presses because I had two hernias and they allow me to go "heavy" without too much pressure on my abdominable wall.
Also, 10 years of soccer have taken their toll on my knees, blew side tendon on my left side.
So the presses give me the limited range of motion, protection and isolation I just can't get with squats. As long as you keep the intensity up you can get a great workout.
I've done whole leg workouts on the presses when I was short of time. I had a press with two angles for feet placement, so I would do Giant sets, 12 reps of feet apart, feet together, lfeet angled forward and then lockout the press and do 25-30 reps of calf raises. Take two minute break and do it again. In 30 minutes you can move some serious weight and really feel it the next day...or at least I can.