The unfortunate fact of the matter is that while I don't think it's like kissing an ashtray (my boyfriend is a very occassional smoker) it's still a pretty gross taste.
I've also found, however, that it's only really noticable if the person has just been soking or has not eaten anything/brushed their teeth/had mints/etc. in between smoking and kissing.
That may just be me, personally, though. I often think morning breath kisses are just as bad, so.
You know what I'd suggest? If kissing does come up, tell him the truth. Tell him you don't smoke and don't really think it's attractive or appealing to be tasting the smoke and that before you kiss you'd appreciate if he chewed some gum or used a mint. It'd also good to lay down some boundaries with his habits so he knows to respect that YOU don't smoke and he probably shouldn't smoke around you, either.
And just be aware that while some people don't have an issue with it (like myself, I don't mind my guy occassionally smoking), if it turns out that it DOES bother you that he's smoking and he's not willing to stop completely around you or before seeing you, then that may be a sign to cut the relationship from there.
But it sounds like this guy isn't a really heavy smoker, and most people, especially when they have others' feelings in mind, are pretty good at cutting back and respecting that.