I like doing half squats as a prep for doing full squats.
In other words, if my squat goal is 350, I will try half or quarter reps at 375 or even 400, then drop down to 350 for the full reps, which *hopefully* will feel lighter. This is a technique I use with squats when gunning for new highs, or to bust out of a plateau.
I think for overall leg development, though, full range squats are better. Some like ATG and some like parallel, depending.