Very occasionally I'll take one stealth puff somewhere, but generally my public vaping is outdoors. (In NYC there aren't many public indoor places you can vape.) If I won't be able to vape for a while (e.g. on a train) I sometimes turn the battery off and suck a few times, hoping the flavor will trick my mind into thinking it got a little nicotine.
A few months ago, I was vaping at the train station near my Dad's, waiting to get in. They can take a few people if we're going in the same direction. A second lady was heading my way so I started to get in the cab. She started screeching
Lady: I can't sit next to someone who's smoking.
Me: I'm not smoking. This is elec...
Lady: But you were. I saw you. I can't sit next to you and go see my grandchildren.
Me: This is an electronic cigarette and I'm not using tobacco flavor.
Lady: I can't sit in the cab with you when I'm going to my grandchildren's.
She got in another cab, thereby saving her grandchildren from thinking she had started caramel macchiato cheesecaking.