I think it is really good to be open about that (not wanting kids) up front. Because so many people DO make the assumption that it is just in the future, then you'll wind up emotionally invested in a relationship and find out you stand on opposite ends of the children issue. Then someone gets hurt. It is better to know up front.
My (now) husband knew from the get-go I had kids from my previous marriage, and that my oldest had emotional problems (we found out later that it was Asperger's - but he knew what the behavior was). But we also dated for 2 years before marriage, and 6 months of that was doing what we called "family dates" so we could all see what the family dynamic would be like. I not only didn't want to get my heart crushed a 2nd time - but I didn't want to have my kids lose a 2nd father.
a parent will always put a child ahead of a partner in the relationship which is how it should be but is somewhat unfair to the partner
We went through pre-marital counseling, too. And this was one of the topics that was brought up. The counselor made the very good point that the husband and wife are the "core" of the family - and so need to be united and strong. So actually it is not good to put the kids before the spouse.
I'm not saying that I would ever jeopardize my children for my husband - but that he and I present a united front for them. We have never let the kids play the "you're just my step-dad" card. I think my oldest child may have said it once (he's 16) and I just turned around and said "ok then" and gave him the same punishment from my mouth that my husband had just issued. Our daughter has never said it at all. (There's still time of course, LOL!)
I just think the big thing for single parents dating is to be real and honest - and to take whatever time they need. It is not that different from dating before kids - you can't go into every relationship
looking to make it THE ONE or else you get hurt too much.
It reminds me a little of couples who have trouble conceiving: the harder the couple tries to get pregnant - the more stressed they get, the harder it becomes. So then the couple gives up, adopts a child, the pressure is off - and BANG - they find out they are pregnant. The big relationships seem to happen like that, when you relax and aren't searching for it.