Reverse osmosis is the lowest level of filtration necessary to get rid of most bad stuff in water, but, that's not enough. Distillation and then reminetalization is the only way to get rid of a lot of the stuff that's the worst like synthetic hormones. 

Berkey lost a big suit. In not sure that they should be trusted to filter out what they claim, especially with their weaksauce excuse that "is too expensive" to do this party testing. They've sold millions of systems, and if they don't have the money to do a few simple this party tests, then they are not a company I would trust at all.