My first labour was induced with synto and came on far too quickly. Gas didn't touch it, but it gave me something to focus on other than the excruciating pain. I felt a bit stoned, but it was more of a distraction technique. With my second labour, I requested it only after I'd begun pushing, DD2 was posterior and the gas helped take the edge off the back pain so I could keep pushing without becoming too overwhelmed by the contractions.

All in all, it was pretty average for me. It didn't relieve the pain so much as gave me something else to concentrate on so I could labour more efficiently.