Mediocre. Don't expect a culinary experience. Expensive for what you get.
My wife and I have been to Symposium twice. Both times, it was busy, which is usually a really good sign of a great restaurant.
However, Symposium isn't busy because it's good; it's busy because there isn't any competition for this class of restaurant in Georgetown.
For the bedroom community that Georgetown is known as, one would expect a range of medium class restaurants for folks who pay 500k on a house to enjoy. Symposium benefits from this by being one of the only dimly lit, seemingly quaint restaurants within a 10 minute drive of the city core.
The trouble with Symposium is that it's "just ok". The laminated, pedestrian menu is what you can find at any chain restaurant. The service is slightly overworked and spotty at best. The prices are slightly more than what you would expect to pay for the quality of the food.
My wife and I might find ourselves here again. However, it will only be as a result of the lack of options in the area.