Our favorite sit down is Carnation Cafe. I have yet to have my Croissant Chicken Club this trip (it's closed due to rain), so I'm going through withdrawals. My spouse loves anything on the menu.
As aristocat said, BB is great for the atmosphere, but, very pricy for the quality. You are basically paying to eat inside of Pirates.
We normally like a sit down breakfast at Riverbelle Terrace, but, with ROA closed, it takes something away for us. Like aristocat, we enjoy soaking up NOS while eating in that area.
At DCA, we actually really enjoyed the meal at Ariel's and for quick service, we enjoy White water snacks in the Grand Californian.
We tend to eat pretty healthy, so places that serve a lot of fried foods don't really appeal to us.
I normally wouldn't do this, but the place I would avoid is the Fortune Cookie (I believe that is the name) in DCA. It's over by Pacific Wharf and it serves what is supposed to be chinese. The rice was so mushy it felt like rice flavored mashed potatoes

in my mouth and the chicken was horrible and dry. In their defense though, we ate there when it was brand new, so they may have improved. I just haven't been able to bring myself to eat there again.
You may want to check out menus at allearsnet.com to get an idea of prices/types of food you are interested in then ask people what they thought of those specific restaurants.?
Hope that helps.