Its an interesting verdict, but its an outlier.
Mobile phones fall into class 2B carcinogens - that is, stuff that can possibly cause cancer, but its a kind of catch all group that includes coffee and carpentry.
Studies to date show very little link between their use and tumour formation, and there is little work been done on demonstrating a plausible mechanism.
Still, if you are a heavy user, with a phone glued to your ear 6 hours a day or whatever, it might make sense to use a headset :)
http://scienceblog.ca...le-phones-and-cancer/