Worked for me, didnt take the contraction away completely but took the edge off thats for sure. I got it when I was 6cms, had DS 5 hours later. It did make me groggy/drowsy/sleepy between contractions. But I was rested when it came time to push.
In saying that it, it worked however I do think it slowed down my labour... as it made me groggy I lay down on the bed pretty much as soon as I had it. If I had been up and active I dont think it would of been 5 hours til I had him.
DS was born alert, with apgars of 9 & 10. I had him at 5pm, and as soon as I had him adrenalin kicked in and all that grogginess disapeared. The first night though we both slept for ages. DS was a lazy feeder anyway, but I dont think it affected him that way at all.