I think the consensus seems pretty clear here.
On a contrary note, I'd like to add that smoking is good for one thing: the people around you. Not the ones real close, they might get get tagged by effects of second hand smoke (if you believe in all that), I mean the ones a little further off who will benefit from the Social Security taxes you will pay, but won't collect on because you'll likely die right around the time you would start getting benefits. It would be your contribution to everyone else's retirement.
So, not to be too sentimental about it, do what you want. Good for you if you don't, good for me if you do...