I tried it with my first pregnancy, but only after a couple of days of stop-starting. I phoned the midwives out of frustration and they suggested lubricating my fingers and stimulating my nipples for at least 20 mins. If i was close enough, it would start things rolling, otherwise, i'd have to keep waiting. So i did what they suggested and sure enough, within about an hour and a half, i started full contractions and had my daughter the next morning. It feels a bit weird doing it, and if anyone was perving through my living room windows they woulda thought i was a bit loopy (especially since i was watching the Terminator on tv! )
I was already 9 days overdue though.

I've tried it with my second preg, to no avail, and i started doing it again last night for this one, as i'm now 40wks and getting stop-start contractions again! Nothing has happened yet though

Like someone else already said, i think it works well when you're really close to going into labour anyway, otherwise, it doesn't do anything. A breast pump would definitely be more efficient than doing it by hand, but i'm not sure if it's the actual nipple stimulation that does the trick or whether it's the entire breast....might wanna check into that.

Good luck!