I've been walking past this place for years, and only just stopped in today. Let me tell you - I'll definitely be back. Ueno just knocked Nari Sushi off the top of the list for best lunch take-out sushi in Corktown.
Located just below street-level of 75 Sherbourne, the service was incredibly friendly, with the sushi chef describing the different pre-packaged sushi rolls on display. I chose a dynamite roll ($9.95 for 10 pieces), and took it to go. Included was a tiny square tray for dipping soy sauce - cute and functional.
Sushi was kept at an optimal temperature - chilled enough to dissuade any health concerns, but warm enough that the rice is still fluffy. You can taste the freshness of the fish, and the ratio of filling to rice is bang-on.
Four stars instead of five, because when I went at 1:30pm on a Wednesday the sushi selection was quite slim. A bit late for lunch hour, yes, but there also wasn't any sign that they were rolling more to-go boxes. I'll try them again next week at an earlier time. Very, very happy with my first visit to Ueno.