I have both my kids drug free but i cant say that i really planned it that way. I actually said with my first that i would take gas but nothing else. I didnt even think about it to tell you the truth. I just got on with it and made every pain a positive pain. I walked as much as i could and slept between the contractions with #1. I was then stuck to the bed with the monitor around me so i had to get as comfortable as i could, but still just got on with it.
#2 DS, was drug free to which is what i wanted again, and thats only because i knew i could do it. I walked again through contractions and made the pain positive.

Everyones pain threshold is so different so thats the teller really. I actually thought mine was low but soon found out it was quite high, lol.
I think the advantage to a drug free birth is that you feel reasonably well afterwards.

Just go with the flow and take what comes. And remember, its positive pain.