Here are a few we know (in no particular order). I've run into Korean friends from the food business at all of them from time to time.
The best bbq:
Haeundae(sp?) they bring live wood coals to your table. the side dishes are non-descript. Buford hwy, outside 285, in a little strip center with an x-rated movie theater.
Asiana Garden, Asia Square, Buford Hwy inside 285. full korean menu, sushi and bbq. definitely a scene. Open late.
Cho Sun Ok. Buford hwy,outside 285, next to Tower Liquors. My longtime favorite for home style, has trended steadily downhill over the last five years. Korean business colleagues from Chicago were recently terribly under-whelmed (they chose it themselves from web references about Atlanta's KoreaTown area).
One bowl meal:
Tofu House. Just inside 285 in an old fast food location. Mostly just soups/stews/jigae's. pretty good for its limited menu.
Lunch or Banquet:
Seoul Garden. Outside 285 about 2 miles in an old Western Sizzler. full korean menu and sushi. banquet rooms.
On my list:
Ilmee (sp?). Cobb Pkwy/US 41 in Marietta. A very small homestyle family run place that multiple reliable reports say is very good for their chicken and squid dishes. On my list to try.
There are a ton more places on the Buford Hwy corridor I haven't yet tried. Reports anyone? In general, I've had better Korean in Chicago and NY.