Before I started breeding, I didn't have a maternal bone in my body when it came to other people's kids. The other posters in this thread are right when they say 'your own are different'. I can deal with other people's offspring now, but before I had mine I'd run a mile rather than hold someone else's newly produced progeny. Scary, noisy, smelly, unpredictable things! Plus there was always the fear of dropping the wretched creatures.......
When my eldest was born, I was scared to pick him up for the first 24 hours (I'm a short-arse and couldn't reach into his crib to get a secure enough hold on him. That's one-size-fits-all hospital-issue equipment for you). Once I got the hang of it though, everything fell into place. I was no longer just me, I was someone's mum. Sounds scary to a non-parent, I know, but it really isn't when you are a parent......
Ap Oweyn is far more poetic than I am (ditto Christopher Hitchens, thanks for the quote PASmith) but they are correct about how one's perspective changes when one becomes a parent. The child becomes one's life, and it feels absolutely right.
Others have said this earlier in the thread, but I'll say it again. Don't wait "until the time is right" - it never will be. There will always be another financial commitment, another career move to take into consideration, and before you know it you'll be desperately scrabbling around to fund another round of IVF before your wife's biological clock runs out completely. I'm not saying "breed NOW!", just think about it now, seriously, if you know you both want children.
My first pregnancy was unplanned and totally unexpected, but it made us think seriously about what we wanted. If it hadn't happened, I might not have children now. And that really doesn't bear thinking about.