We tried the all you can eat sushi--inexplicably called Funky Sushi--at Nooshi on 19th Street NW (the new name for Oodles Noodles). I would call the experience a definite success...the sushi is not the best in the world but it is certainly quite good and the price is right and the system works well.
The offer($20 or $25--depending on the range of sushi you can choose among) is good every evening from 5 to 8 pm and the deal includes miso soup, appetizer of the day and ice cream for dessert. You are given a laminated sushi menu and a marking pencil...you give your order (as much as you want) and it comes in a large dish. If you want more, you reorder.
Service was very attentive even though the first plate of sushi was a little slow in arriving. Special mention should be made about the attractiveness of the plates, bowls, etc.
I definitely plan on returning.
NOTE: Checking some of the reviews of Nooshi tells me that the owner of Nooshi also owns Spices and Yanyu...pretty good pedigree.