Fresh fish is great, but be aware that some varieties do have elevated mercury levels, and should be consumed on a limited basis. I don't have the types of fish or recommended dietary allowance, but I'm sure someone will be along shortly with that info.
This is sort of on the same subject, but I effing love
I tried it for the first time about a year ago, and I am addicted! I would much rather go out for sushi than have a cheeseburger, pizza, or any other junk food! I think it's kind of cured me of my former love of junk food. I can now pass by a McDonald's, or a get whiff of those fries, without so much as a wistful glance.
That being said, I know some of the rolls, especially the tempura fried ones, aren't that healthy so I try not to have it a lot. Also, the sodium isn't so good for me either, but it's better than downing a fat-soaked burger!