I never had a problem nursing in public, but a lot of people have been supportive. The very first time I nursed in public, I was out at a restaurant with my parents and newborn. My mom urged me to nurse my son in the booth and said no one would even notice or be able to see anything. I've had a lot of strangers be sweet to me. One time, flying home to see my family with my 12 month old, we had a hellishly delayed flight layover. I was sitting in the terminal nursing my son, and a middle aged lady walked up to me, smiled, and handed me a bottle of water (since nursing makes you thirsty). I've always thought that was just the sweetest way to quietly support a nursing mom.
Oh, also, I took my baby to work with me for six months. It was a small, tight-knit office. One time, one of my coworkers said, "Hey, that baby's head is blocking my view." (In retrospect, I know that sounds inappropriate, but we were good friends and it was hilarious at the time.)