From what I have seen (and saying it works or doesn't is a vast oversimplification) it appears that there are some completely un-understood benefits to acupuncture for treating some conditions, however, I haven't seen any real studies that compare it to traditional Western medicine. It seem to be good for chronic pain more than anything else, especially the kinds that the Drs also can't find a specific cause for, at least from a quick glance at these results.
Information about acupuncture, including its safety and effectiveness in treating pain and other conditions.
www.nccih.nih.gov