I did hypnobirthing and breathed DC2 out (I'd had a truamatic birth with DC1 resulting in forceps, episiotomy and a lot of subsequent issues that took a while to heal/fix).
It was a really beautiful experience and I honestly didn't push - I just focused on my breathing. Apparently I was completely calm and silent. The baby was born with absolutely no intervention; I only had gas & air, and no tearing. At the time I was doing it, it felt like the most natural thing in the world. I felt as though I would be doing the baby a disservice by forcing her out via pushing hard. I recovered amazingly quickly - was home within a couple of hours, felt fine and was on a high for weeks afterwards. It was completely different from my first labour, where I struggled to walk or sit down for weeks on end. I bled less the second time too.
BUT labour was progressing very well and she was coming down the birth canal all on her own anyway. I wouldn't have been able to breathe DC1 out because the baby was lying in a funny position, got stuck, the cord was round his neck, his heartbeat was all over the place, as was my blood pressure and I was seconds away from having the kind of c-section where the doctors have to push the baby back up the birth canal and remove it through the abdomen (can't remember what it's called and it sounds absolutely awful).
So what I'm saying is - I recommend hypnobirthing but I don't believe that it can work if there is a complication with your labour. So if your baby is breech, for example, or gets stuck, hypnobirthing can help you stay calm and deal with the pain but you're not going to be able to breathe out a baby that's got stuck....
I guess that what I'm saying is, give it a go, it can be wonderful, and I believe that it is far less traumatic for the baby BUT don't set unrealistic expectations for yourself; sometimes nature intervenes and we can't control every aspect of childbirth! If you end up having to push the baby out, or having some type of medical intervention, you won't have "failed."
That's my opinion anyway!