I have discovered that most anti-open carry sentiment comes from people who have never tried it, and usually from gun restrictive states as well.
I open carry everywhere, every day when I am out and about. I have open carried in places such as Pike's Place Market in Seattle and SEATAC International Airport. I open carry a Taurus PT-145 with stainless steel slide in a Fobus Paddle Holster with passive retention, so basically everything of the gun behind the trigger guard is completely exposed. I open carry in clothes that are completely average - usually jeans with no holes, something just "above" a t-shirt like a pullover polo shirt or button up western style shirt and tennis shoes.
In my experiences, and those who I have met with who open carry every day agree, open carry is a great public relations tool, at least in Washington State. It provides Joe Public with the visual image of normal everyday Americans doing normal everyday American activies who just happen to wear a gun as a tool for self protection. If Joe Public doesn't SEE us doing this, then all that they will see is the anti-gun image provided to them by the Brady Campaign and anti-gun media.
In day to day life, about 98% of the public population has no reaction at all to the gun, probably don't even notice it. About 1.5% have a positive reaction to it. I've gotten everything from verbal thank you's to thumbs up signs, to people asking questions about why and legality and going away with a more positive idea/attitude than before. Only about .5% of the public that we encounter in Washington have negative reactions. 4 out of 5 of those negative reactions come from concealed carry only "pro-gun" people that tell us we should cover up our gun.
I think a major issue we have in "gun politics" is the fact the we, as gun owners, are so willing to treat the gun like it has some inherently evil properties about it. All this talk of telling a police officer about your gun during a traffic stop when not required to by law because it will make them feel better, talk about asking for permission to bring your concealed carried gun into a friend or relative's home when visiting.
I think a lot of positive PR would happen if we simply treated the gun for what it is - an inanimate tool incapable of evil on it's own that has a specific use just like the jack in your car or cell phone in your pocket. I wish that we would quit believing that the gun somehow has evil attached to it as an object, which is what the Brady Campaign has been shouting from the rooftop for decades. Treat your gun like an expensive cell phone - take sensible personal precautions against it being stolen/falling into the wrong hands and other than that treat it no differently than your cell phone. I don't feel the need to hide my cell phone away because soccer mom by be upset at the sight of it, I don't feel the need to tell a police officer or friend about my cell phone at first opportunity, and neither do I feel the need to do those things with my gun, either (unless required to do so by law, of course.)