For the official report from the European Commission Health and Consumer Protection Directorate-General, which concluded that there is "no evidence for special health benefits of Tahitian Noni juice which go beyond those of other fruit juices" see here (pdf download).
The Mayo Clinic state here that:
"Noni juice has gained popularity as a tonic for everything from arthritis and depression to heart disease and cancer. But there's no evidence that noni juice is effective in treating any of these conditions."A study was undertaken at the University of Hawaii and sponsored by the National Center for Complementary and Alternative Medicine into the effects of Noni juice in cancer patients that ended in 2006 but no results were ever published. I wonder why?
Finally, there's a good summary of the facts here.