I'll second Murasaki and Kotobuki. I also like Raku in Bethesda alot. I went there last night with a couple Japanese friends and they really liked it. The funny thing though is while I prefer the more traditional stuff, they are more interested in the Americanized stuff, like Philly rolls, since they can't get that in Japan. The one tradtional item we got--sea urchin nigiri--was very good and my Japanese friends agreed. I've been to this place a few times and never had a bad experience. Their non-sushi items are really good too.
I plan on trying Sushi Ko soon...