I use adblocks, so all I see of dKos is the central diary and the right hand diary list. The ad list disappears, which is a good thing, because when it's there it annoys me no end.  

I don't much like the unstretched centre-justified design, because it wastes a lot of space.

But that's more a problem with the narrow dKos version than with a centre justified design in general.

Centre justification otherwise is fine. It's where your eyes naturally spend most of their time when you're looking at a monitor, which is another reason I think it makes sense to put the bulk of the information there.