We had a very disappointing experience. We arrived and despite having reservations and a half full restaurant, it took 10 minutes for them to set a table. When we finally were seated it was another 15 minutes before anyone came over with water. We waited another 10 minutes before our server arrived and took our order. We really should have left before ordering - if you've sat for 25 minutes without anyone even stopping by to at least say "I'm sorry I'll be with you in a minute", you're probably in an unprofessional place. The setting is beautiful, but the food itself was just ok. Also - despite touting itself as a 'farm to table' and 'slow food' place, there was virtually no information given about the food itself in the menu or from the wait staff. Were the ingredients raised on the farm property? Is the fish and pork local? Based on what we ate, it did not seem particularly fresh and I would doubt it was local. On top of everything else, this place is just WAY overpriced for what you're getting.
There are plenty of places around the DC metro area with nice views that also serve great food and provide excellent service. Try 2941 for a special outing for instance, but avoid Patowmack Farm.