The menu at Kellari is seafood-centered menu, and several fresh fish are available (grilled) each day. The grilled Dover sole was excellent, very flaky. Yet, at the price that I paid ($40) for it, there should have been some roasted potatoes or frites served alongside it.
I started my meal with a bowl of the classic Greek soup called Avgolemono, and it was fine but not impressive. I'd give it a grade of a B.
I was told that Kellari's baklava was exceptional, but it was one of more bland baklavas that I've ever eaten -- not as flaky as baklava typically is, and the sweetness seemed to smack more of sugar, not honey. The flavor lacked sophistication.
I really liked the dish of diced radish, hummus and olives that was served gratis as a kind of antipasta-appetizer. The hummus tasted great on the grilled bread that was served with it. There is a good, diverse selection of wines by the glass, including a few Greek wines.
Although Kellari is a very nice space, the price point is going to be a stretch for anyone who isn't on an expense-account lunch. Those kinds of lunches are still had in the K Street corridor, but it's a limited market. And the food I ate didn't "wow" me enough to make the price point seem reasonable.