I don't understand the bad reviews Naan gets. I have eaten here almost monthly since it has opened, and I have had uniformly great experiences.
First, the sushi is great. Get there during happy hour, and the prices are pretty good. It is expensive at other times, but what I really like are the rolls: rich man's roll, vocano roll, SMU roll, etc. They look and taste different than other sushi I have had in Dallas. The super tataki and unique roll in ponzu sauce are also awesome, and the rest of my family loves the ahi tuna tower. I have also tried the rice bowls and enjoyed them as well. The only thing I did not care for was the new seafood pizza, but wanted to try something new.
Second, my service has been good. The servers have always been attentive and responsive in my experience. From looking at the reviews, others have not. I do agree that this is not a place to rush through your meal.
I also ate here when it was the Geisha House, and this is a big improvement.