It's a tricky question.
I found babies and toddlers overwhelming: the noise and the relentlessness. I expected that though. I have never regretted having them but for me it is definitely getting more enjoyable as they get older and we can talk about interesting things, I see their personalities develop more and it's not an epic mission just to leave the house.
On the other hand, it's harder now they have problems I can't fix for them, which was not the case when they were tiny.
I think the PP who mentioned social structures is spot on. I am a lone parent, and that has made life very different to what I envisaged. I think with a supportive partner and family around, the experience would be very different and there would be a greater level of freedom sometimes therefore motherhood wouldn't feel all consuming, whereas 95% of my time is spent on work and children. It would be nice if there was some space for me as an individual in my own right. And what I wouldn't give for a week in a nice hotel next to a sunny beach, all on my own! That said, I know I'd miss them horribly even for a week.
My life has much more purpose now and I wouldn't change it. I just hope they think I've done a good enough job of raising them when they're older and look back. With two parents to split work and time with DCs I could have been far more "present", not always rushing around, and that makes me sad as I haven't been able to spend as much quality time just being with them while small, as I would have liked to.
But no, no regrets.
I can absolutely see why it's not for everyone though. To do a good job of parenting you have to be prepared to be quite selfless for a long period of time and some people quite understandably don't want to do that, and enjoy the lives they have without children.