There is sufficient scientific evidence. There should be more, but a number of surveys have been done—one that includes 19,000 individuals all across the world—which show that, over a period of time, 81% of them have been able to completely stop smoking and switch to using electronic cigarettes. So yes, I believe that the evidence is there. It would be good to do more research on this, but it does help, absolutely.
On November 27th, 2014. See this statement in context.