I eat at Apres Diem about once every couple of months, and I always want to like it. The food is usually fresh and slightly Mediterranean (which I like), and the atmosphere is always abuzz with young people of various flavors and persuasions eating in the courtyard. (You can also watch people in line for the nearby Midtown Art Cinema, which is usually interesting, too.)
It's one of the few menus in town that's decent for grazing, with very good sandwiches and decent salads and cold appetizers along with the (slightly expensive) dinner specials.
Last night I had the baba ganoush plate and my dining partner had the Greek salad, and we were both very happy with our food. However, when we were ready, it took thirty minutes to get the attention of our server and pay our check. This was on a Tuesday night, when it wasn't particularly busy, and it's not unusual. I'm afraid that this is relatively common there -- it's a great place for a light meal, to hang out with friends, or to enjoy a bottle of wine or a coffee drink, but be prepared to linger over it.
By the way, the restaurant shares ownership with Carpe Diem in downtown Decatur (larger and slightly more formal) and with the Carroll Street Cafe in Cabbagetown (smaller and much more informal), and many of the menu items are the same. I eat at Carroll Street much more often, because it's simpler and quicker and the food is just as good.