Big fish. Beware: if you're looking for a place to be waited on hand and foot, this is the wrong place. It's all about the fish. Big pieces of fish that completely cover the rice underneath, and touch the surface of the plate.
This is sushi in what I've heard my friends describe as "the Korean style" -- everything is bigger. Sometimes the nigiri takes two bites to finish, which is a big no-no to traditionalists. But what can I say? I'm into good fish and zero ambience. Nagano fits the bill, and it's pretty cheap.
Try the "hamachi toro," which is something I've only seen on the menu there, and appears to be the fattiest part of the yellowtail. It's way better than regular yellowtail, and only a little bit more pricey (and way less than toro).
Best rolls in SF -- consistently fresh fish I started going to Nagano shortly after they opened. I've always found the staff to be extremely friendly, and I cannot rave enough about their fantastic rolls and sashimi. Excellent value for price. Be sure to try the No Name roll and the Dragon Roll, which is exquisitely presented.