I breastfed my 2 year old in the middle of the Monterey Bay Aquarium while I was 9 months pregnant. I got a few kind of surprised looks and that was the most extreme reaction to all of my nursing in public. To be fair it was kind of funny looking given how big my stomach was. :)
I nursed for more than four years straight including through a pregnancy and tandem nursing for 8 months. People were really nice to me. I don't think anyone even ever told me to cover up. I never owned a nursing cover. I was one of those tacky non-discreet people.