I think it's good to have a plan - when I was labouring I was on a whole other planet and found it hard to communicate with the midwives (which is strange for me!!) and so it wouldve been helpful! (I didn't have one) It was hard for me to stick to what I wanted (no drugs) when I was offered pethidene etc - I guess I just felt more pressure or something iykwim?? Anyway it was all ok cos DH was there to speak for me when I couldn't and all went "to plan"!!
Hope this helps lol!!