A new, expensive, multi-year study shows some isolated cells could be affected by cell-phone radiation: The study, the authors freely admit, doesn't necessarily apply to living organisms, as they were testing the general principle of whether electromagnetic radiation in the range found in cellular telephones--orders of magnitude above the energy given off by a Wi-Fi cards and access points in the home--would damage cells. It did. Cells had their DNA uncoiled a bit and couldn't always repair themselves. In a biological system, however, other mechanisms might compensate.
I hope that more studies of this scale are conducted to provide more definitive information. It's clear that there is no smoking gun: there are millions of people who have had the kind of exposure--especially to older, more powerful cell phones--that would show an outbreak of disease if the effect was anything but extremely small. But measuring risk and understanding how to mitigate it is always a good idea.
For myself, I don't expect that cell phones will show any real risk for adults, but I won't let my tiny boy use a cell phone (when he's old enough to talk on a phone)--if there is any substantial risk it's more likely to affect developing brains. I use a Bluetooth headset for 95 percent of my talking time. Bluetooth puts out less signal strength than Wi-Fi, even.