I am a sushi addict. I have had sushi in 15 states, all of the coastal states in the West and Florida, Georgia, Louisiana in the east - states close to the coast. But some of the best sushi I have ever had is right here in Reno.
Reno is nearly the sushi capital of the US. There are I believe more sushi restaurants here per capita than any other city (unverified but seem to remember reading it in the paper here). And almost all of it is all you can eat. And all of it is fantastic. Well some places have rolls I don't like and crappy service and are priced too high, but the quality of the fish is top-notch.
Simply Sushi in Salt Lake is a Reno transplant to SLC (here it is Sushi Pier), but I was not impressed at all with their fish or sushi or service. Sushi Pier is far better. But there is one in south salt lake that is the best I found in SLC, and it is all you can eat.
Sushi Yah. < click for details
Sushi Yah is also a Reno transplant (here they were Aloha Sushi, since changed owners and not as good) and they have typically the freshest fish I have had in the valley. Unique and varied rolls, and lots of them, great nigiri, good price (19.95 i believe for ayce). They also run a restaurant in Provo-Orem area but cannot remember what they call it (don't think it is Sushi Yah though). When you go to the one in SLC you can ask John, the owner, about their location in Provo.
In Reno typically the all you can eat places have fresher fish because they cycle through it somewhat faster. I have found this to be true at Sushi Yah. In Reno we also get spoiled because we are within truck distance of San Francisco in about 4 hours so the fish is always great. The one thing I never liked about Sushi in SLC is that the fish tends to have a slightly salty flavor, especially salmon. It is legal to transport raw fish cold but not frozen in various salt solutions and still claim it is "fresh" to help it travel. It affects the taste and can also affect texture especially for very lean fish (like tuna) and fatty fish (like salmon) tend to impart more of the salty flavor. Never had any issue with that at Sushi Yah.
Try it. I think you will like it.