Truth be told, my own personal experiences with nuns were limited to the surly, old crabs at my church when I was growing up. It seemed to my young mind they really hated life on this earth. Many old priests I remember were very much the same way. Much of my impressions of nuns come from my parents generation..... hearing stories of kids getting beaten with rubber hoses for writing with their left hand. High school girls called wores in front of the class (by nuns) for wearing nail polish. Students getting slapped across the mouth with hands or rulers for correcting a nun when she was clearly wrong. That's one big reason I went to public school (even though my teachers were almost as bad
). It seems like things weren't a whole lot better in my generation, my sister-in-law (who's as quiet and polite as can be) was pushed backwards down the stairs because she went up the wrong side and slapped more than once for asking questions the nun couldn't answer.
I'm guessing you don't hear stories like this any more simply because the Catholic church was forced to change it's image due to people leaving that church in record numbers.