We had a great time in DC staying at Ehab's apartment. It's really well situated, just 10 minutes walk to Georgetown and about the same to the closest Metro. Having Trader Joe's at the end of the street is really useful too.

We were a group of four - two couples - so the apartment worked really well for us. Not sure whether it would necessarily work so well if you have small kids, as there are stairs to one of the bedrooms and the kitchen.