Last month's Journal of the American College of Cardiology has a meta analysis of 11 studies (10 geographic sites) where cigarette bans were implemented and researchers used this natural experiment to determine the impact on heart attacks.
Harvard full-text link (requires HU login)
The impact is impressive! In the ten communities, rate of MI decreased by 17% (confidence interval from 8% to 25%), and the decline continued with subsequent years of observation. The impact was most pronounced for the young (which means more averted years of life lost) and nonsmokers.
This is strong evidence indeed -- and a good example of a community-wide intervention that can save lives (and costs) AND improve care.