I think there are more that regret it than you think but are terrified or embarrassed to say so. The few people I know that have admitted it have gotten soundly trounced for saying such a "horrible" thing. And most that I have talked to it's not the child so much as the timing, the other parent and/or the massive responsibility they regret.
I have known since I was 12 I didn't want kids. I'm 39 and still have not felt this biological clock that people speak of. For me I had to raise my brother and I learned one thing: I truly do not think it's possible for me to love something that craps, pukes, pees and eats all the time while screeching at the top of it's lungs. The nighttime feedings OMG and if the baby is has health issues like my brother
His immune system was compromised so he was sick all the time. The doctors didn't figure out that he was allergic to lactose and needed soybean formula until about a month before he came off his bottle so his tummy always hurt. That kid could cry for HOURS!!! He would literally scream until he turned blue, we'd rush him to the hospital and they'd tell us it's colic and send us home
Also our mom is bipolar and unmedicated. I'm bipolar and so was my sister. I could never take the chance of being like our mom or passing this on. No child should be raised like we were. And I'd love to say I could never be like her but I know for a fact that she said the same thing about my grandmother(ALSO bipolar and unmedicated) and I know how that turned out.
Then when you figure in I can barely take care of me, I'm lazy and I loathe being a caretaker it's no wonder i've never changed my mind and never will. What I really love are those people that tell you "Oh it's the greatest joy you can ever know. When you hold your own child everything changes for you and it's a love you've never known. It's not possible to not love your own child." All I can think is if that's true child abuse wouldn't exist but what do I know?
I think making a pro/con list is a great idea. Be completely honest with yourself about where you are in life, what YOU want out of life, whether you are prepared for the financial burden, how is your support system etc....
Also be very aware of Postpartum depression if you do decide to have a child. I've known 6 different woman that had it and the symptoms were missed because they hid it.