The stadium in vegas has clearly been built as a multi-purpose venue. Its quite impressive.
After all, its going to host all of about 10 NFL games a year? But I could see it being used for things like UFC, boxing, concerts, even massive conventions. It's in a good location - just south of the strip and near the airport. It will need to stay busy to justify that cost.
I was also very impressed with the one in Qatar that will be dismantled. If a success, it would be a great idea for Olympic games and world cups etc.