"How dreadful!" cried Lord Henry. "I can stand brute force, but brute reason is quite unbearable. There is something unfair about its use. It is hitting below the intellect." ~ Oscar Wilde - The picture of Dorian Gray
No kids, no plans to have them. I haven't definitely decided no, but some serious problems would have to be sorted out. I'd have to see myself as the type of person who would be a good parent, which means I'd have to be in good psychological health, have some strong social ties, confidence in my abilities, and feel a real sense of enthusiasm and purpose in being a parent. I would have to be started on a real career path and financially independent and stable, and I'd like to be in a long-term relationship with the right person. None of the above is true right now. If it doesn't all become true at some point while I'm still young enough to have kids, then it's best that I remain childless.
I don't think it's a tragedy either; both people with kids and voluntarily childless people say they're happy with their decision. People can be satisfied in a variety of circumstances.
there have been a few times when i've thought about the long term implications of bringing children into a reality in which exponential population growth is the bane of the world's resources.
on the flipside i adore children and i might end up drawing cute punnett squares with someone someday-- guessing what phenotypes i might pass on. I may have a better answer for this in about 9 years. The only definite is that i'd only reproduce to replace myself and a potential partner.