Actually, yes. I read Bicycling Quarterly's Paris-Brest-Paris 2007 survey; they concluded that riders with generator hubs, while slower, are much happier with their lighting system than riders with battery-powered lights.

Unfortunately, this being my first year of randonneuring, I don't plan on making such investment just yet. I'm just going to work mostly with what equipment I have, which when coupled with careful planning, should be more than adequate up to 600k.