I used the Epi-no.. but only got to 7cms as bubs came 3 weeks early! My OB recommended it, and said he's seen it improve (possibly shorten) 2nd stage of labour for many, and of course reduces the need for episiotemy etc.

Tallon is my first baby, and my 2nd stage went for 1hr, and I only had a graze. Not sure if the epi-no helped or not, coz like I said, I only got to 7cm. But it makes me wonder how my labour would have been if I'd got to the 10cm tho!

As for permanently stretching the muscle... I haven't had any problems with those muscles down there, even post-birth I was pretty much straight away able to hold the 'squeeze' for the 10secs 10 times.. which is what I was told to work towards. The epi-no can also be used to strengthen the muscles tho, it's not just for stretching the perineum.