For the money, you can't beat Ru-San's ala cart or their 11am-2pm buffet. $1.00 california rolls(3 pcs), $1.50 rock'n'rolls(3 pcs), and $1.00 nigiri(1 pc). If you go there I recommend the Cajun roll, the Spicy Tuna roll, the Spicy Aoili Scallop roll, these are all $1.00 for 3 pieces.
I've heard MF Sushi was pretty good but I've never been there. There is a place called "Sushi Yoko" off peachtree industrial and 285 that has good sushi and more traditional Japanese food, there is also a Japanese grocery store attached to the side if you want snacks or instant ramen bowls or whatever.
Ru San's may not be the best sushi in Atlanta(depending on who you ask) but it's not the worst either, I'd rate it a 75 out of 100 and it depends on that particular days experience, sometimes they are 100 out of 100 with the quality of the fish. Also the quality varies between the buffet and when you order piece meal. The reason we like it is because 2 people can load up on Sushi for about $20.00-$30.00 including tip where as other places your paying $6.00-$8.00 for one roll (4-6 pieces) and $2-3 for nigiri (1-2 pieces). The buffet is like $12.95 and has fried calmari and other stuff besides sushi.
If you want to spend a lot of money on a trendy place they just opened up a Geisha House resturaunt here, I forgot what that area was called (morning brain fart). I think you would be paying more for the trend then food you are getting at this place though as it seems very pricey for sushi.
We don't eat sushi as much as we used too though, we got sick of eating it so much and asian food in general. We'd always have Korean BBQ or Japanese or Tofu Soup. Now we keep going to The Highlander for their burgers and specials of the day, last time we were there they had this awesome catfish stuffed with a crawfish stuffing on a bed of spinach in a lemon butter sauce, Gordon Ramsey would be all giddy and shit. It was really good and amazing if you consider this is bar food technically.