A blue post that caught my eye

To be clear: On your first kill of a boss in normal difficulty, you are guaranteed a random rare and a class rare, as well as some blues and other stuff. All other kills on all difficulties result in standard drop probabilities. You have a decent chance of getting a rare or two every time you kill a boss.

So will it still be worthwhile running though multiple times? I think not, the gold drops and value of the low end items reachable will be negated by the higher value drops of later levels. The excessive farming of the Skeleton King in beta was also achieved by a waypoint co-op "exploit" which is likely to be fixed rapidly if not already, and even if it is not it is unlikely to be advantageous at higher levels than Act 1 Normal.

For more blue posts about DIablo 3 check out the blues tracker at http://www.diablofans.com/