Don't count on them instead of birth-control pills. )
Men can get impotence issues if they smoke too much. I don't think it is a matter of not having the sperm, but not being able to get an erection. Frankly, I've known a lot of male smokers and have never heard any of them complain that this is a problem for them. (Well, maybe one, but he is 70 now and so it might not have been the smoking.)
I have never heard ciggies affect women's fertility. Just make the babies have low birthweight and some other things you don't want.