Furthermore, just on the basis of the number of single mothers I know, I would posit that at least one man you know has kids, regretted it, left the mother and just hasn't volunteered that information to you.
[edit] Also, my wife was adopted when her parents were in their 40s, so it's probably not too late to raise a kid.
The hard part is that parenthood changes people in ways that go beyond life experience. There are actual, measurable physiological changes that happen to parents. In many ways, children are like a drug to their parents. Just like addicts will sacrifice much of their lives to their habits, so too will parents sacrifice much of their lives to their children.
So asking your question is like asking whether a drug addicts wants another hit. That person will undoubtedly want one, but the person that person was before their addiction might look at the reality of the situation and decide they didn't want to start the habit in the first place. Likewise, someone not 'under the influence' of their parenthood might look on the situation differently.
But, in both cases, it's impossible for someone to understand both sides of the choice simultaneously.
Besides, regrets tend to come in the form of "wish I've done something" (this applies to both sides), as can be seen even in earlier comments of this chain. Regret of having kids is likely to manifest in the form of wishing to have done more/ different things.
But to follow on my other comment above, I also have a pretty clear idea that I gave up some things to become a parent. And I think people who skip having a kid, and then feel doubts later in life about that decision, are really just feeling the other side of that coin.