This isn't just the best sushi in Pittsburgh, it's the best representation of Japanese food, period.
Not only do they get the food right, the ambiance is spot on as well. I stayed in Japan for a month and the atmosphere absolutely reeks of Japanese sensibility. Slightly cramped and personal but not too personal.
The sushi is divine and it's been described a million times before me. Each piece is a perfect cut and perfectly constructed. The temperature is just below room temp so it melts in your mouth. The ingredients are some of the freshest in the city.
Don't just go for the sushi. Try some of the other dishes, you might be surprised and like them. The inclusion of fried chicken, while seemingly odd, is an accurate accoutrement in Japan.
Love it, love it, love it.
Lookit my review for more. http://eatinginpittsburgh.com/2011/02/17/rodzilla-reviews-chaya/