I usually go to Sushi One (in Causeway Bay on Leighton Road) for sushi. It's good and the sushi is decent. I never go for midnight sushi (half price after 10pm or something like that?) since there can be a bit of a crazy que but lots of friends enjoy doing that.
A couple weeks ago I tried Sushi O on Bridges street and while the food was good it was a bit expensive. I did enjoy trying a couple different dishes which I hadn't seen on other sushi menus.
Last night I tried Monster Sushi which has just opened in the basement of Causeway Bay Plaza 2 and I really enjoyed it. The setting was similar to Sushi One (and some of the staff had even moved there) but I found the sushi much fresher. I think the price was a little more expensive than Sushi One but I definitely enjoyed it more.
What's your favourite sushi restaurant?