I thought the majority of locals didn't want it there?
Many of us don't, in fact, Im not sure who wanted them here(aside from local buisness owners, hotels, and the City of Chicago for the extra taxes)
I have had mixed, but mostly good reviews about ecigs and the city.
Police - I live by two coffee shops(although one closed down very recently) and before it started to get cold out, I would frequently pass cops and they never said a word(although a couple of looks).
People on the street - I have had more questions like "Have a light" or "can I bum one(they assume tobacco cig)" than anything else
Bars - no real problems some questions, but I tend to frequent same places.
Restaurants - dont do it here. My personal preference.
Stadiums - Cubs no issue for me personally (have heard others say they get asked to put it out)
Bears - Got asked once not to do it(steelers game) and it was by a person sitting two rows behind me. I continued just less obvious and all other times no issue.
As with all places, just dont blow huge puffs of vapor in enclosed areas like a restaurant and no one will care(for the most part).