Here's a chart with nutritional info, but I don't know how good or bad it is:
More information I found:
Sushi Nutrition -Low in Fat-
Sushi is low in fat and is a very nutritious food. A typical setting of 7 to 9 pieces contains about 300-450 calories. The fish in sushi provides protein and can be a good source of omega-3 fatty acids. Vegetables are a great source of vitamines. Seaweed is rich in iodine. And rice provides complex carbohydrates.
More info:
The real (low carb) diet killer with sushi is the rice, one little cup of which carries with it 145 g carbs. Anyone who has eaten at a Japanese restuarant, whether you had sushi or not, will attest to the likelihood of your eating at least one cup of rice. So beware.