One problem with every study is who's funding it. Researchers are generally begging for money, so they wouldn't want to embarrass the corporate interest funding the study. Same goes for labs commissioned specifically to do a study (in this case, the results are more likely to be buried as the person paying for the study owns the data, which means the lab may not be free to publish the results).
So expect a study funded directly or indirectly by one or more cell phone manufacturers to conclude no definitive link, while studies commissioned by someone keen on proving a link to conclude there is some sort of link.
Call me cynical