I had a similar experience as AFWife. With #1 I had gone through transition and was fully dilated and effaced, but contractions were pretty weak and after a long time, not sure how long, I still didn't have any urge to push. My midwife asked if she could break my water, she did, with much difficulty as my membranes were very thick and tough, and I immediately felt the urge to push. It still took 2.5 hours to push her out though.
With #2 when I was fully dilated I told the same midwife to go ahead and break my water, she said it was very thick and tough again. DD#2 was born within a few minutes.
I have in my birth plan for #3 that I would consent to having my water broken again if in the same situation, but not before. I really didn't feel like it was a big intervention, and my body's reaction to it told me that it was the right thing to do, but with all the risks I would probably avoid doing it before being at least very close to fully dilated and effaced.
That being said, I have been having very strong, frustrating, and tiring prodromal labor and have been considering getting my water broken if I am pretty far along and it seems like contractions are dying down again... But have not made any decisions about this, and hoping I won't have to! I've been reading up on membrane rupture and what I have read makes me nervous about doing it early.