I used the tens machine from very early labour onwards and as the contractions got very strong I decided I wanted to try the bath for pain releif as it wasn't enough on it's own. I had to take the tens off to get in the bath.
I honestly think if it wasn't for the tens getting me through the majority of my labour I may have had to ask for some drugs as I was thinking in my head I want something - then it was time to push.