My back is tight a lot of the time, and I did hurt my back on this exercise a while back. My form looks much better on the heavier stuff than it did before, but, obviously, I have room for improvement
I'm doing box squats nowadays. I'm really weak off the box. Also, I have a hard time squeezing my glutes to get my hips going in the movement. I'll have to work on that so I can get the good carryover to front squats.