I'm 39 weeks today so just started using mine two weeks ago. I obviously can't attest yet to its effectiveness during labour, but it has given me an idea of what the stretching of the perineum will feel like when the time comes, and I'm hoping that will make the real experience less scary/shocking.
I use the epi-no every evening for about 10?15 minutes, then follow that with another 10 mins of perineum massage. Both the epi-no and the massage are awkward and a little uncomfortable at first, but I'm finding it's getting easier. I've also found that I get a better result if I lie on my side when using the epi-no. In a half-reclined position, I found I had to really focus on holding it in with one hand; if you lie on your side you can hold it in place more easily by closing your legs over it. Lying on my side also makes it easier to read a book or something to pass the time. :)
When I started two weeks ago, I was able to go to about 5?6cm. Now I'm at around 7?8. Really eager for baby to make her appearance, but wouldn't mind a few more days so I can see if I can get a little closer to 10cm.
So in summary, I think I'm pleased with the results so far, if only because it's taken some of the mystery out of what that one aspect of labour might feel like. I'm really hoping it will help avoid a tear, too, so I can come back with a rave review.
Spending time in the water (bath or birthing pool) and pushing very slowly once the head crowns are also supposed to help the perineum stretch more easily.