All in all, I'm happy that we did end up having kids, but if I could go back through my life and rearrange things in some godlike way that let me still marry the same person and have the same children, I'd definitely have kids earlier.
I feel like it's hard in my 40s to have the same energy that I did 10 years ago, and raising kids is definitely something you have to pour energy into. Also, my mother died a year and a half ago, in her mid-70s, and I really feel like both she and my kids would have benefited from having longer together. My father is 80 now and while he remains healthy, it seems very unlikely that he'll actually see his grandchildren grow up. My father-in-law died when his first grandchild was an infant.
I think it'd also be nice to have my late 40s as a time when I could really heavily concentrate on my career because my kids were old enough to handle a lot of the small day-to-day things by themselves, since this feels like probably my prime earning time.
None of this is stuff that makes me say, "I screwed up, I should have made any sacrifice to have it different." Overall, life is great. But if you're 28 and you're thinking, "I could go either way -- wait a decade to have kids or have them now," I'd personally recommend "have them now."