Acupuncture and pain

Anyone have any comments about this article in the latest AANA journal? I thought it was very interesting. Anyone with any experience with this, seeing this, etc... One of my good friends is a chiropractor that regularly does this, but we haven't actually discussed it. Is pain relief achieved solely via endorphin release? Or is it voodoo? Or some other mechanism? This article lists a number of possible chemical mediators.