Tough choice on the answer! First, I've not had to think about dating anyone for 15 years now so I had quite the little smirk thinking about it.
Next, I think the answer to the question would be based on how secure they were in their sobriety. I'd be too afraid to date someone who was on the fence at all. I'd be too afraid that if they slipped that I'd then say "what the hell" and go ahead and drink. It doesn't matter how secure I am I still know that I could be coerced.