I have had 2 very different experiences with acupuncture in preparation for birth. The first was a wonderful woman in Newcastle who does Japanese acupuncture. She burns beautiful oils and plays lovely soothing music whilst you lie on a specially designed table for pregnant women. The needles didn't hurst and she was fantastic. At no stage did she say her treatments would bring on my overdue baby she simply said it would help me relax and give my body the best chance at reaching a labour ready state. She also did guided visualisations with me to help me 'see' my baby coming down and getting into position.
Then with my second birth I saw a very well known acupuncturist here in Melbourne. It was in a noisy busy sports medicine clinic, the needles hurt terribly and actually left bruises for 2 weeks. I hated it and did not go back for my third visit. I gave him 2 chances as I thought maybe it was just a bad day the first time. He also guarenteed me I would be in labour in 24-48 hour, I had my baby a week and a half later!

Do your research and find a practitioner that 'feels' right. It can be a really special experience.