Before we all get carried away
Before we all get carried away, it's not as clear cut as some may paint.
Firstly, there are some proposed non-thermal non-ionising mechanisms of interaction.
Secondly, the Interphone result taking stopped in 2004 - the report authors have been fighting amongst themselves on what conclusions can be drawn.
Thirdly, the other serious epidemiological study (by the Hardell group in Sweden) found statistically significant increased occurrences of some cancers in the brain. Not massive increased in risk (roughly doubling I think for some). Twice a very small risk is still a very small risk, but it still raises more questions than it answers.
Fourthly, both Interphone and Hardell studies have many, many failings, neither is anywhere near conclusive.
Fifthly, the latency of existing studies has not necessarily been long enough for anything to show up with statistical significance. Hardell seems to have risk increasing with exposure latency.
Barring anything revelatory (of which there has been none), the conclusions of the widely approved Stewart Report should be followed. Keep exposure as low as reasonably possible, and try to minimise children's use of mobile phones (numerous scientific reasons mean if there is an effect they will experience it far worse).
In conclusion? We need to keep an eye on things, as billions of people worldwide could be affected. It's probably worth paying less than a penny per person who would be affected, to reach a stronger conclusion than "we don't know, but we aren't panicked".
There are numerous reports available from scientific journals (PubMed, sciencedirect etc) that provide detail. I'm yet to see any good coverage of these Interphone results in the media. Sorry El Reg, normal standards not adhered to here.
(Personally I'm not worried by mobile phone use, but too many people are overly dismissive without being familiar with the conclusions in the scientific reports. See comments above, and no doubt, below.)