I am on day 2 of smoking my e-cig and still smoking. Yesterday I only had 2 smokes and today I plan on having just one. I am having a hard time giving up the morning smoke.
It was instantaneous for me with my eGo Tank - before that, I had a cigarette-looking thing from loong-totem that sufficed for giving me a fix in no-smoking places (airports, movie theaters, etc) and when it died, I upgraded to an eGo.
I put out the cigarette I was smoking when the first battery came off the charger to try it out. I haven't lit another cigarette since, haven't even wanted to. With proper gear, it's totally effortless.