One important note about Sushi in Stockholm...it's a little bit more pricey than in North America! But the fish is usually very fresh and there's a nice consistent quality to all the sushi restaurants in Stockholm.
So try not to convert exchange rates in your head and just enjoy fresh sushi at one of the many restaurants found all over the city! And since there are so many, we won't be able to list all the good ones fairly. But there is one famous hole in the wall restaurant/kiosk near Medborgplatsen Station (on Folkungagatan) that does come highly recommended.Enjoy!