I think with breastfeeding tops it depends on the style and also how big your boobs are. I never got on too well with trying to feed through the little slit type tops, as I am rather large chested. I also found the tops that have no "modesty panel" a total nightmare, as I probably exposed more boob trying to feed in them than I would have in any normal top. Nursing vests are ace, as they are so easy to feed in. Some tops have underlayers and wider openings at the side, which are great for keeping your tummy, sides and back covered. Also means it is so much easier to whip up the top bit and feed with no hassle. This was my absolute fave top whilst feeding urban wrap top and these are just great, no slits, just panels which open angel jersey top .
I'm really not a big fan of nursing covers in public, because I don't think breastfeeding is something you should have to "hide", and also they really do tend to draw more attention than pulling up your top and feeding ever would.
If you feed in front of a mirror, you quickly realise that all most people see is the baby snuggling up to you, and people don't really take much notice anyway. I have never had any negative comments when bf-ing out in public, and have fed my DS and DD whilst on planes, in restaurants, shops, shopping centres etc etc. I have to say friends who bf said it's more the thought of what comments they may get, than any actual comments they have received that makes them anxious about feeding whilst out and about. They have also never come across negative comments either.
Whilst you're new to breastfeeding it sometimes takes a little while to build up confidence, but once you are both used to feeding it is so quick and easy that it's not really an issue. I am definitely not one of those women who can just whip out a naked breast in public and get on with it!! That said, I worry more about people seeing my wobbly tum than my boobs, as the baby covers them anyway!