I've only had one issue, it was when DD was about 3 months. An older gentleman refused to even talk to me, lol, instead talking to my sil. He asked if she was my friend and she said, "yes, she's my sil, why?". He replied "you know they have a special room for that". I was sitting right next to her and I said, "you know, I don't have to use it, right? And you know I can hear you, right?". He walked away mumbling.
That said, I've NIP so many places! DD and I travel a lot to see my family in CA, she's been on tons of airplane trips, a cruise, she's just a little world traveler.
Anyways, airplanes have all been great, even the last two when she's been over one. People around are usually very nice. If you want a seat empty on SW, the trick is to nurse your child as soon as you get on, you'll be avoided like the plague. LOL, I don't mind the extra room.
I had no problems on Carnival Cruise Lines, or in any of the places we visited (Costa Maya, Cozumel and Grand Cayman).
I've nursed many places and most people never even bat an eye. I keep waiting for someone now, since DD is 15 months, but so far, so good.