Travsi wrote:

"...thats why you see alot of track bikes (in the velodrome) with quite a bit of slack."

I wonder if the serious track racers don't see slack as a way of avoiding even the slightest mechanical drag.

When I adjust my chain I can make it so tight it creates noticeable rotational drag.
As I loosen it, at a certain point I experience a sudden and significant reduction in drag.
At that point, the chain has no visible slack and no delay in forwards/backwards impetus.
If I loosen the chain further I detect no increase in smoothness nor quietness; if further loosening the chain further reduces mechanical drag it does so in such a tiny amount I can't detect it.
I test the chain on the work stand by spinning the rear wheel up to full speed with the pedals and then letting the whole system coast down to a stop.
If I've got it right it spins silently and coasts forever.
Presently, my chain has no visible slack and no noise; it coasts forever; and, it gives me instantaneous braking and feedback.

I ride fixed for the control and precision and not for the speed.
I like the "steamroller" sensation and I lose that with a slack chain.
Perhaps if I raced at a velodrome I would put some slack in my chain.