The back squat is relatively new to me, compared to the front squat, as we didn't start doing it until last Spring or so. It always makes me a bit nervous (not as easy to dump the weight), so up until last week I've been working only the front squat.
However, about a week I decided that I would like to start training with competition in mind, and the back squat is the only one accepted. I had a power-lifter watch my form today, and I maxed out at 180! I thought I was more around 160, so I was really excited. She also said my form was pretty good - and that I was breaking parallel (which is required). I think I might have had another 5-10lbs in me, but like I said, going heavy on the back squat makes me nervous. I'm looking forward to getting more comfortable with the lift and moving some real weight around!