Kids notice things that adults don't. Not sure why, and I don't think the fact that kids are more at eye-level with an open carried firearm is the reason. When my kids were little, they would notice when I put a new box up on top of the frige. Nowhere near their eye level. Hoping it was a box of cookies I guess.
Mostly, people are oblivious to open carriers, which doesn't say much about their situational awareness.
As far as I can recall, I've been "noticed" open carrying three times in the last 12 years to the extent that the "notice" prompted the individual to say something to me. One was a woman in the now closed Fudruckers in Annandale. I used the event as a teaching opportunity and she went away satisfied, as far as I know. The second incident was in a Home Depot where one of their employees or contractors approached me with a "survey" (meaning a sales attempt). She noticed my visible handgun and asked my occupation. I replied, "business consultant". She said, "Really? I was wondering because your thang was hanging out." Well, my "thang" does that sometimes, I guess. I gave her a little briefing on open carry and she went away happy (but without a sale).
The third event was much more problematic. In January of 2007, I was open carrying (fully in compliance with 18.2-308 as it existed at the time) at Tony's Pizza in Manassas along with 6 others. A self described retired Marine noticed us, and exchanged some hostile words with several of our party. He finished his dinner, and called 911 from the parking lot. I listened to the 911 recording (FOIA'd days after the event) and came to the personal conclusion that he was trying to get police to respond with maximum force. I think the current term for what he was trying to do is "swatting". About 6 Manassas and Manassas Park officers responded. Most didn't know the law regarding concealed and open carry. Two of the officers were aggressive and behaved in a grossly unprofessional manner. The rest were merely unprofessional, doing nothing to restrain their more aggressive and misbehaving colleagues. One officer cursed at me personally several times. Cops bullied the owner of Tony's into asking us to leave, which we did.
In addition to the 911 recording, the FOIA brought to light emails and radio/text traffic among the responding officers. Some of it contained additional profanity and derogatory commentary, so much so that the city of Manassas apparently had to briefly disable the bad language content filter on their internal email system in order to respond to the FIOA.
Several of us wrote about the incident on OCDO and to VCDL. I think I can claim credit for naming us the "Tony's 7". Its been long enough ago that its hard to find anything about the Tony's incident in OCDO archives, or anywhere else, but one post is here:
http://forum.opencarry.org/forums/showthread.php?36314-Update-on-Tonys-7-3-23-07
About 400 open carriers showed up at the next Manassas city council meeting. Two of the seven (myself included) filed formal complaints. I was never contacted or interviewed by police regarding my formal complaint. The chief's official response ignored the formal complainants and was addressed to VCDL's Philip Van Cleve. I simply got a copy of it in the mail. In that response, the police chief pretty much completely white-washed the conduct of his officers during the incident. A smaller group of about 200 open carriers attended another city council meeting to protest the chief's white-wash. Nothing much happened after that, at least not officially. The good news is I haven't heard of any subsequent incident in the last 6 years where open carriers have been harassed in Manassas. Can't complain about that result.
So, in short, I've had 2 innocuous and positive events where I've been "noticed" open carrying and one that was more stressful, but probably good in the end.
I would add that I believe open carry is very important. While the decision to open or conceal carry is a personal one, I believe gun owners should, from time to time, make a point of open carrying just because we can, and while we still can. A right we're afraid to exercise because some believe it's not good tactically or because it might make people uncomfortable is a right that has been LOST. I'm not going quietly into the night and allowing the loss of any more if my rights!!