I had a debrief when I was about 35w pg with dc2, so about 2y after dc1 was born.
It was fantastic. Incredibly worthwhile. I didn't even nknow I needed one until I did the hospital tour (both dc born in the same hospital) and the mw noticed that I was getting quite angry. I wasn't losing it, just behaving in a well-mannered, repressed, British way, but I think that woman really knew her job! She offered me a one-to-one meeting.
We spent about 2h going through my notes, she explained what had happened and why, as far as she was able to. She was honest and forthright about it all, saying "That should not have happened", no attempt at making the hospital out to be right and me wrong. She listend to me, accepted what I had to say and how I felt about it. Was completely non-judgemental.
Afterwards I felt so much happier about the forthcoming labour, and confident, too.
The most important thing she did was to effectively give me permission to say "No." Which was what I did. When I turned up in labour the same two midwives greeted me as had been there with my first baby. I said to one of them "I want you and only you. I don't want her to come anywhere near me." My wishes were respected. Labour no2 was a good and satisfying experience.
Yes, ultimately, having a healthy baby and healthy mum is the important thing about labour. But how you feel about yourself is a very important part about how you function as a mum - as well as all the other aspects of being you. And how you feel about your labour can have a major effect on how your next labours go.