After being bullied by former partners through my teens and early twenties, I used to think I wanted kids. But after finally being able to get a hold on my own life and what I want, I have realized that I don't want kids. Not right now and not "someday." However, I recognize that I might change my mind in the future, when my biological clock starts ticking or whatever.
For some reason, though, the idea of adoption sounds better to me than having my own children. Maybe it's because I don't want to put my body through that hell, and maybe it's because I don't want to add more kids to the world when there are already so many out there that I could help. Also, my genes are pretty shitty--I don't want my kids to be forced to deal with my bad allergies, mild asthma, terrible eyesight, and genetic predisposition toward a number of unpleasant things.
If I'm pushing 40 and still not feeling that biological clock, I probably will adopt. (Or at least try, ugh. My depression would probably make me an unlikely candidate.)