To be more anecdotal about the OP, in my experience, it’s been financially and socially fantastic to have a baby in my later 30s (my kids are 11, 9 and 18 months). We’re financially on solid ground and I bought a somewhat ridiculous stroller to celebrate the pregnancy (we had just the one $2,000 car and I bought a $400 jogger–silly, but so much fun!). The big kids are in school during the day and adore their baby sister and give me parenting tips. They take a lot of the load off of me of entertaining her on car trips and other times. (We spare them the less enjoyable tasks.) My middle child is impatiently waiting for the baby to start talking more. Also, we finally have a house of our own, and we finally know a lot of people and I have a number of chums with kids the same age as my kids. It was so much fun to have pregnancy buddies for the first time in my life–two good friends had babies that same year. And my sister is even having a baby this year!
In contrast, when I had my first two at 27 and 29, we were living in an expensive area that we couldn’t really afford (but I hadn’t figured that out yet) and I barely knew anybody else with kids. We had initially envisioned having 4-6 kids, like our Catholic peer group, and I’d envisioned my oldest daughter being my right hand girl. Well, that didn’t happen, especially not when she was 2 and 3. It was all I could do to keep her from finishing off baby brother. I’m glad we did it, but we had a number of tough years (6, to be exact). And one grandpa was very unsympathetic and kept saying stuff like, “Women with 5 kids do just fine. Why is Xantippe having so much trouble?” He had never had 2 under 4, ever, but I digress. And as I discovered some years later, my oldest was mildly autistic. As it happened, my oldest (and second child) eventually grew into the helpers I had envisioned, but it took way longer than I thought–namely the better part of a decade.
The other aspect of this is physical and medical, which has definitely been way worse for me as a later 30-something. I had a miscarriage with my 3rd pregnancy at 36, and was just so surprised. I theoretically understood that it was a possibility, but at 13 weeks? How was this even possible? My 4th pregnancy was a sort of tour of pregnancy unpleasantness: 1 trimester nausea and heartburn (totally normal), 2nd trimester bleeding, subchorionic hematoma (never even heard of them before) with a 30% chance of losing the baby, short bedrest, rest of 2nd trimester on physical restrictions, 3rd trimester gestational diabetes (4 sticks a day and a diet that was effective but had me losing weight between doctor’s appointments) and sciatica. I spent the last 6 months living like a queen bee doing almost nothing but eating and gestating. Everybody did just fine, but I have to ask myself–is doing this again really such a good idea? If I got pregnant again and anything like that happened (and the internet tells me gestational diabetes has a fairly high rate of recurrence), we’d have to hire a nanny for me and the toddler, which is ridiculous.
So, to summarize, my experience has been that socially and financially, older parenthood is FUN!, but the medical and health side were terrible. It was the best of times, it was the worst of times.