I have a new favorite: Momo Sushi & Cafe on Queen Street. Everything was super fresh. Their rolls were especially tasty. SO liked the St. Thomas roll (spicy tuna and the whole thing tempura-fried) Their nigiri was wonderful, tamago was a little thin though and I don't think they give you miso soup and salad gratis like other places, but wow -- their fish! And it didn't cost an arm and a leg!
Distant second place: Bonsai Grill on 23rd in Crystal City - Inconsistent, but when they have good stuff, they really shine. I think the switch in management/ownership caused the decline in quality.
Honorable mentions: Osaka in this random stripmall next to Springfield Mall
(don't laugh) Matsutake in the DCA Airport. (Service was excellent, and they have had the freshest uni I've had in the DC Area)