While there are loads of Sushi restaurants in the Bay Area, for our money the best combination of quality and value on the peninsula is Koma Sushi on El Camino in Menlo Park. Last night for the first time since we've been going there (10 years at least), the uni was not up to snuff. We mentioned it to the chef/owner and he immediately went in the back to get a new batch and served us up another order.
For about $75 two folks can go first class with all of the specials and cold saki. Similar meals would be at least double at two other local places: Fuki Sushi and Kigetsu.
So give Koma a shot if you're on the peninsula. But get there early - especially on weekends.