I live/work in DC area so I'm biased, but its a good city. Has the hectic, party, social scene if you want it, but its also a place you can step back an enjoy a slower pace of life if you want that. Nightlife/restaurants have really exploded in recent years and I'd say we're probably one of the top 5 places to eat out in the country right now. Overall quality of life is very good for a "big" city.
Traffic can be bad but also can be avoided. You can live in the city or in the very close burbs and have little to no commute. Most of my co-workers walk or bike to work. Metro system is good. I think its much more diverse and dynamic than ATL/Raleigh.
The main downside is the cost of living. If you're looking to live in a nice place, save money and enjoy all that the city has to offer, you need to make well over $100K. DC may be behind only NY and SF in terms of cost of living...