I had one a little over a year ago. For me, the worst part was when it was making it's way through my kidney. I ride a commuter coach to work, and it started just after I got on, so I had to sit there and deal with it for 45 min. I knew that what was going on was localized to my kidney, but I didn't think it was a kidney stone. I thought a stone would cause a really sharp pain, but it was a really intense dull pressure, like my kidney was being squeezed in a vice. When I got to the hospital, they put me on a morphine drip and the nurse remarked that the pain intensity was comparable to childbirth. Passing it was not pleasant but much easier than I expected, although the percosets probably helped with that.