The Yakitori house is a great place for a quick bite, but as others have said, not really a place for sushi. Also , they have been known to 'run out' of items later in the evening. The miso soup is also not that great, IMHO.
Another place to consider is the sushi place at the Swan. Not exactly quick service prices, but the sushi there was very good. You CAN usually just walk up to the sushi bar (Though I think it's pretty much only open in the evenings) for a sushi fix. I think it's open rather late too.
As far as the Contemporary, it is far from quick service prices overall, but you can sit in the bar area without a reservation (if it isn't full) and order some sushi. The sushi wasn't especially inexpensive, but the rolls were fairly large, as I recall, and the sushi seemed to be one of the better values on the menu from what I observed.