Tamasei Sushi, Noe Valley
Tamasei opened up about 6 months ago and I'm astounded not to see anything about it on Chowhound yet. Though it isn't exactly a destination sushi restaurant, it's a really nice addition to the smattering of neighborhood sushi places in Noe Valley and is in the same spot as the old Matsuya (24th and Vicksburg). I've been a couple times since it opened and have always gotten either the sushi special or the sashimi omakase - both are quite solid. There are often excellent specials like slightly smokey-tasting bonito sashimi with a hint of garlic or clean, refreshing hirame with a nice ponzu dip. This place has all the little details down- excellent sushi rice with just the right texture , tasty (though probably not homemade) oshinko and miso soup that tastes like it was made with homemade dashi, for example. And the atmosphere is just right. It really feels like a cozy neighborhood sushi place somewhere in Japan, with a nice older couple running the show. It is a pleasure to sit in the rather small, cozy space and listen to them talking back and forth to each other as they prepare and serve the sushi. All in all, a much nicer and far more authentic spot for sushi than either Amberjack or Hamano, which both get a lot of mentions on CH - though it *is* a little pricier. The only downside is that it can be closed for long stretches of time when the owners go back to Japan for some reason or other.
Omakase is a great deal at $25 (!!!). If I'm feeling hungry, I might get a bowl of rice on the side and maybe some oshinko.
As for being closed unpredictably, who knows? It seems like a lifestyle thing for them. You'll walk by and see a sign in the window that says they're in Japan for Obon or for a butoh festival or something. It's usually around 10 days or so.