The Journal Spine published a paper in May 2009 looking at the effectiveness of surgery for low back pain. The doctors who did the research were from Portland, Oregon.

The researchers concluded "For radiculopathy with herniated lumbar disc, we found good evidence that standard open discectomy and microdiscectomy are moderately superior to nonsurgical therapy for improvement in pain and function through 2 to 3 months."

So over the short term it looks like discectomy is effective, but the benefits diminish with long term follow up in some of the cases.