The last time so far was in 2000. I hurt my back at work and had a lower discectomy. They removed parts of 2 vertibre(sp?) and then cut out part of the disc. I will say that after I woke up from the surgery it was instant relief from the pain. I actually looked forward to the surgery to get the pain over with.
I had almost the same thing when I was 14. It took the Doctors months to decide what it was because 14 year olds don't get Herniated/Slipped discs. Well 6 months and 1 quack Doctor later, we find a doctor who knew exactly what it was and I had surgery the day after Christmas and you are right, the surgery made the pain go away INSTANTLY. It was the physical therapy that hurt after that.
Then 18 years later(last Summer). BOOM back problems again. Only this time they treat it with Steroid/Cortizone shots. So far 5 shots and I am begging them to just do the surgery again so I can get some relief.