Hi lemontwist,
I would suggest keeping your relationship and your quit as separate as possible.
Right around the time I began quitting, I started dating a guy who hated smoking. In fact, I was still smoking part time when we first started seeing one another.
I was honest with him about the fact that I was a smoker, that I was working towards a full quit, and that I was uncertain of whether or not I would succeed. That type of honesty is simply 'how I roll." The rough agreement that we had was that I would not smoke around him. I would also shower and brush my teeth after smoking if I wanted to get anywhere near to him. (He hated the smell.) In exchange, he would not nag me about my progress. (I knew that would be counterproductive for me.)
He offered to be my "biggest cheerleader." While he was supportive of my efforts to quit and was willing to listen to some of my monologues about the addiction process, I also got the feeling that he didn't quite get it and would soon tire of my stories. Talking about smoking and quitting and all the steps in between just wasn't doing anything to enhance our bond, and it made me feel kind of weird sometimes. That is a big part of why I came here--to talk to other addicts who share some of my understanding. After that, I would tell him of my progress from time to time, but not much more.
Here is another touchy area in the whole smoking/ relationship thing. I didn't want my relationship with him to get too intertwined with the idea of me quitting. I really needed to quit for myself. And I really needed the goal of quitting to separate from the relationship. Otherwise, any rockiness in that relationship might encourage me to relapse. I didn't want to start smoking again because I was mad at him or because I felt we were going to break up and there was no point to the quit.
I am really, really glad that I kept my quit separate from relationship. As fate (or my attitude) would have it, I broke up with him just a couple of months after my full quit. Because I had maintained the mindset that my quit was 100% for me, the break up did not derail me. In some ways, I may have even been more determined to keep my quit right after the break up.