It seems that if there is any article about nursing in public, someone always posts "I'm okay with it as long as the mom covers up". Usually they mean with a nursing cover or a blanket.
I tried using a blanket once, when Emily was 2 months old. My dad was coming into town and I felt a little odd nursing uncovered in front of him. I got over that really quick since Emily is a warm kid, and she was not comfortable under the blanket.
Especially before she started solids, we nursed in public a lot. And I never covered up. Usually Emily would pull my shirt down so I wouldn't show any boob once she latched on. I'm sure I've flashed some people when she unlatches, but I'm usually pretty quick at covering myself.
Nursing in public is a great thing, but I feel bad for those moms who are given a hard time.