Yoshi's is located in Jack London Square in Oakland, right underneath that massive parking structure. The place is definately gorgeous. It's designed to look like a traditional sushi house in Japan. They even have traditional seating (sitting on the floor on pillows and mats) if you're interested.
The food however is mediocre. The sushi is definately fresh, but the prices are not so friendly. California Rolls are about $8 each, so if you're planning to fill up, expect to pay a lot. They do have great desserts though. I highly recommend the Green Tea Ice Cream
The sushi house is also directly connected to a music club. You can buy your tickets in advance and while you're dining, the staff will reserve your seats for you in the club, so you don't have to hurry and eat.