I've given a fair shake to Koishi and been three times just in case I had a bad experience. I had heard that they had authentic sushi and so when the Adventurous Palates group decided to go there, I was in. We got a very wide variety of rolls, soup, apps and entrees. Some of it was good, most of it was OK. I went back another two times with my husband and I wasn't blown away by the quality of the fish any of the times i went and found it very very average.
The service was not too bad with the big group but when it was two of us it was slower, oddly. And unfortunately it feels like you're in a renovated Pizza Hut.
Bottom line: The service, food and environment all left a bit to be desired. Will you hate your experience there? No. Will you love it? No. For me, not worth the drive unfortunately.