It's a completely unanswerable question, OP. For an ordinary 'a lot of people do it a lot of the time' experience (rather than, say, going to Mars or being world famous or something), I can honestly say that in my experience having a child is utterly unguessable-about unless or until you do it yourself. Which is why it's such a difficult question to explore, because you can't know it unless you do it, by which time it's too late to back out (which is of course why you're posting!)
I'd never planned to have a child at all, and was quite content, had lots of frank close friends with children and am the eldest of a big family, so very familiar with other people's relationships with their children/their highs and lows, and the logistics of looking after babies and children. Then I finally decided, after a year or two of dithering with DH, to have a child, and our son was born when I was 39. And while on the one hand I'm exactly the same (careerist, not particularly maternal) person I was, and my priorities have been added to, rather than changed, being a mother 'feels' completely different from the inside to anything I'd imagined beforehand.
And it feels different to how it looks, too, because (as I'm well aware, having been childfree for a hell of a lot longer than I've been a parent), having a child often looks like pure boredom and drudgery from the outside, because all that's visible are the bedtime routines, missed sleep, dashes for childcare pick-ups, and standing resignedly reading a magazine while your toddler tantrums in the frozen food aisle.
Whereas the good stuff is largely invisible. All my siblings are childfree by choice and my sisters in particular make no bones about how they feel sorry for me, which is annoying, but probably entirely understandable. It does often look like that. Sometimes it also feels like that, but it's far from the whole story, and the whole story is weirdly difficult to communicate because it's both mystical and desperately cliched.
I suppose what I'm trying to say is that it's a leap of faith, however carefully-researched and considered. And that I'm absolutely certain that, unless something very fundamental had changed in me, my life without a child would have gone on being interesting and fulfilling, like my sisters' lives.