My gripe with the leg-press is a gripe that I have with most machine-movements:it takes away from the coordination and focus of training.
Now, now, before everybody starts ripping me a new one, simply think about it:in a squat, you have to be in there 100%, because if you slack, you could get a very serious injury. You know that, you feel the weight "crushing" you, and you give it your all, because a failed squat is not what you`d like to happen.
In the leg press, you`re going through a quite fixed movement...sure, you can press a shitload of weight, but you can also look at that sexy girl training her adductors whilst doing it, think about something else etc. You don`t feel crushed by the press, you can get away with less than 100%, IMO.
Body-through-space free weight movements tend do produce systemic results in my personal experience:better coordination, maybe improved posture, almost always improved training-focus etc.