I enjoyed Koishi. I actually worked across the street for quite some time before I tried it out this year. Yes, it is an old Pizza Hut, but the ambiance is nicely low-key Asian. I was with a group and I found the sushi was good and the price point excellent, My group enjoyed their selections.
Not the biggest sushi rolls, but tasty and the service was friendly as well as timely. I would definitely return for future visits.