I had peth when in labour with DS followed by an epi a while later. The peth did basically nothing for the pain but made me relaxed and happy in between contractions. The epidural took ALL the pain away and I slept until it was time to push. I couldn't feel myself pushing and so was very ineffective and DS was ventouse.
For DD about half an hour before she was born I had remyfentanol (sp)? Highly highly recommend it. Took the edge off the pain, gave me something to focus on (pressing the button to deliver a short-lasting hit) and made me feel pretty good in between contractions. Ask your midwife/OB about it.