My favorite counter services are Plaza Inn and French Market in DL, Earl of Sandwich in DTD, and Tangaroa Terrace in DLH. I'm kind of ambivalent about the CS locations in DCA (Flo's is okay), but if I was trying to pick something that wasn't a TS location, I'd go with Carthay Circle Lounge (more pricey than a CS, but good appetizer style foods). I also really like Jolly Holiday in DL, but that's more for snacks and other goodies.