The pp pretty much summed it up.
My dd's K teacher last year showed us samples of my dd's class work. (You know, writing letters of the alphabet.) She would comment on how it was good and that the mistakes (like backward letters) were age appropriate. She had also just completed assessing the children's reading ability, and that was when she made us aware of exactly how strong a reader our dd was. (My dd couldn't read when she started K, and I knew that she made a lot of progress in the three months before the conference, but I was really shocked about how strong a reader she was and I hadn't realized it.)
She also told us whether our dd was getting along with the other children, which was useful to know because I really had no idea.
Finally, she let me ask my questions. I had a lot of questions, which is why my conference took more than the full allotted 20 minutes, but without the questions, the teacher covered everything very efficiently in 10 minutes.
The conference was very pleasant, and if anything disruptive was going on at home (new baby, divorce, etc) then it would have been a good opportunity to make the teacher aware of the situation.
The fall (november) conference, I was told not to bring my child with me. For the spring (march) conference, the teacher encouraged me to bring my dd because she knew that I would be driving from very far away and that child care would be difficult because the children get dismissed early on conference days. (My dd just sat reading a book and didn't pay attention to what was said.)