I am very happy with Shimano Generator Hubs. I have two bikes that came stock with Shimano: '05 Specialized Globe (good hybrid bike but heavy); Bianchi Castro Valley ( lighter commuter 10kg);
Yes, there is a noticeable drag when the lights are on. With lights off there is no discernable drag.
Why would someone need a generator hub? Commuting into work from September thru April, at 5:45am is dark. I tried rechargeable battery powered lights but there was too much to that routine.