What would be involved in changing from steam to hot water?

heating?They both use radiators .I ume the pressure valves would have to be removed from all the radiators.I notice there does not seem to be as great a selection of boilers for steam heating systems and that is why I am interested.I am getting ready to replace a older oil boiler and would like to get a more efficient system that runs on natural gas.Anybody done this and is it worth the trouble?or just stick with steam