Oishii isn't fast food--it's good food, fast. I've stopped in for lunch on multiple occassions and enjoyed each menu item I've had. I'm partial to the rice bases of their bowls, but I've also tried a few of the bento boxes, sushi rolls, and the bi bim bap. Always receive my food in a few minutes with a smile to boot.
I've never eaten on location, I always order to go, but the restaurant seemed cleaned albeit small! Price for lunch was always under $10 for me, usually around $7-8, so it wasn't something I'd buy every day. Portions are well worth the cost though. Great value over at Oishii.