For me, feeding is a quiet time for mom and little one. I prefer not to be in a mall or other loud place during times when mini-me (his nickname thanks to my husband) is likely to want a meal, and can plan my chores and running around those times. I will kick back in the back seat of the car with the radio on low, go to the ladies lounge, or even ask a clerk if I can tuck into a dressing room (if at a department store). While I'm discreet if I do feed in public, and most don't even have an idea what's going on, I just don't find it enjoyable to be shopping or eating while my son is hanging on my boob. Sorry if that's not the in-thing to say in this day and age, but it's my preference.
do I have an issue with women who do feed in public? No, it's their choice. Men who have wives who breastfeed who see women in public don't gape and stare, usually they realize what's going on, the eyes usually soften a bit at the thoughts of their kids and wife, and they continue on their day. The unmarried 20-somethings are still at the gawky age of realizing sexuality and are more curious than they care to admit mainly because they and their siblings were bottle fed, but it's part of growing up in an age where formula has virtually replaced mother's milk. The 20-somethings who grew up in breastfeeding homes with younger siblings seem to understand what's going on and accept it for what it is.
So with that, I can say that I don't have issues with seeing a woman's breasts in public, but I tend to be somewhat conservative in sharing my breasts with others. I try to be sensitive to other's comfort level, but don't hide the fact I breastfeed.