I just went to OZ on Korean in business class, and it really is a long haul, especially when you know that there are much more direct options. ATL-ICN-SYD on KE is something like 14 hours to ICN and another 10 down to Sydney (with a nice short connection). But considering that the more direct ATL-LAX-SYD is about 5 hours to LAX and another 14 1/2 to SYD, and it doesn't seem all that bad.

The unfortunately thing is that KE's fleet upgrade process is moving along slowly, so ATL-ICN and ICN-SYD are equipped with the current/old equipment, and no date has been released for the switch to the new planes. So, either bring a laptop/DVD player or sleeping pill, or be prepared to watch whatever is on the main screen for 14 hours (which, FWIW, could include a Korean movie).
One option, if you have a couple more hours to kill, is flying through ORD or SEA (or even select JFK and LAX flights) and get the new equipment with AVOD to ICN, although still the old planes down to SYD.
FYI, per koreanair.com, the seat pitch in economy is 33-34", which is pretty good, especially compared to the 31" on the Qantas 747 and 330 (per seatguru), so that's gotta count for something.

If miles are more important than time, and perhaps comfort/IFE, as BumpMe says, KE to Australia is the way to go.