My best friends discovered Koi while I was away in London. It’s very very good. Even in the off season, the sushi was fabulous. There is a good selection of sakes. The standard fare is actually quite affordable (but not cheap). However, the chef is an artist and it’s easy to get carried away and order more and more of his specialties. The only other potential problem is that the space is limited, so I wouldn't recommend going with a group larger than 4 (although, you might be able to push it to 6). Otherwise, I highly recommend.