Yes, I have been accosted by the police while open carrying. I was eating dinner in a restaurant when an officer approached me. We went outside (first mistake, when he asked for me to step outside with him I should have said no). He lectured me for a few minutes about how I was scaring people. I finally relented and showed him my ID and CPL (mistake #2, I was under no obligation to show him ID or the CPL). He threatened to have my CPL revoked (a bold faced lie aimed at intimidation, against a state statute in Washington called Coercion).
I finally told him I was done with the discussion, if he thought I was breaking the law, then just give me a citation, otherwise I was going back in to finish my dinner. Once I called his bluff squarely like that he gave me back my ID and CPL and told me to go back inside. Then he proceeded to strong arm a less than 18 year old waitress into letting him kick me out of the restaurant. I paid for my meal and left, still open carrying my gun the way that I always do.
The next day I hand delivered a letter to the restaurant explaining what happened and expressing a desire that they honor the rights of persons to have the means available to defend themselves. It wasn't five minutes after I left the restaurant that they called me back, apologized profusely, explained that they did not call the cops and that I was welcome back any time with my friends, my family AND our firearms.
I wrote the police department a stern letter warning them that their officer was guilty of Coercion, and he overstepped his bounds greatly by removing a person from private property without any evidence of a crime being committed and with no desire on the part of the property owner to have the person removed. I also informed the chief of police that we would be having an open carry luncheon in the same restaurant as invited guests of the restaurant and he and his officers were welcome to join us if they desired.
The weekend following my incident about 12 of us open carriers from the area had a great luncheon in the restaurant and no police showed up. I try to go back a couple times a month to eat there and recommend the place whenever I can.