I made a custom superflat in creative mode using seed -6310548451344270339 (I used one layer of bedrock, one layer of clay). Spawn point is at (x=288,z=592). I created a fence grid on the chunk boundaries to determine where exactly slimes spawn.
Available "slime finder" utilities (see http://www.minecraftwiki.net/wiki/Slime#Slime_Finding_Tools ) show valid slime chunks at (x=272,z=576) to (x=288,z=592) and (x=288,z=592) to (x=304,z=608).
On a normal world, these chunks do successfully spawn slimes. On this superflat, though, no slimes spawn in these chunks (see red-marked areas in pic). Other slime chunks appear to work fine (left side of pic).
So are these valid slime chunks? Or is this working as expected, but the slime finder utilities have an outdated algorithm, or are missing an exception for superflats? If so, can we have the corrected algorithm? Was this due to the slime spawning changes made in 12w25a?
(Search found a possibly-related closed ticket,
MC-9440, but without the detail and pics)