I haven't but I personally wouldn't use 1 1/2 reps for something like squats. My sticking point is coming out of the hole, so I'd rather do full squats and then box squats to help with the bottom portion.
In my opinion, 1 1/2 squats don't help as much as something like 1 1/2 lat arm raises. I'd save my energy for deadlifts, leg raises, bulg split squat, or something else that'd have more carryover than a half rep squat.