Just to further the discussion and add more confusion, I'll expand on my experiences.

I don't know how FB gets away with such little slack.

I have some bikes where I was fortunate enough to be able to achieve perfect (measured) chain line. I installed a brand new KMC Z410. If I adjust the slack to 1/4 inch up from straight and 1/4 inch down from straight, totaling 1/2 inch of slack, it feels like hell and I can hear it making it's way around the sprockets. I can feel it in my hands in the garage and my feet when I ride it. My experience is that just because I can move the chain a half inch, that doesn't mean the chain is free to naturally relax and exploit that range on it's own. If I then adjust the chain to the point where there is visible droop, all sounds vanish (dead silent) and I can't feel anything while rotating the cranks. Huge real world difference. I've used the round shank of a screwdriver while rotating the cranks to attempt to ride the chain up and off of the front and rear sprocket and I can't, even when really trying hard to coax it off.

I'm not saying that FB (or anyone else) is wrong, I'm just saying that ALL my chains exhibit an audible and feelable state of mechanical happiness when they are allowed to be very relaxed.

I'll add this. Most chain adjustment advice runs along the lines of, "As little slack as possible, without creating tension." My approach (came from Dad) is from the opposite school, "Plenty of slack, without the possibility of derailment."