The other day...
I saw a slim kid in the gym performing barbell squats, and I was impressed with his form. He's probably one of the only 5 people I've seen in the downtown gym actually drop down all the way. Granted, he was squatting 135 but that didn't stop me from walking over to him and giving him props for executing squats correctly.
For me, the squat exercise goes down as the most humbling workout experience I've had to suffer. My form used to be shit and I shamelessly cheated. The sad fact is, I knew at the time I was doing it wrong and that I was cheating, but pride prevented me from correcting my form, since doing so would mean dropping the weights significantly. I believe it's said that the general different between "cheat squats" and proper squats is about 80 pounds, and that wasn't very far off the mark.