In theory its a great idea, but the reality is, there are some of us that work Sundays and have to travel through those areas. If transit was better on the weekends, and ran early enough...I would never drive to work. But shutting down all those streets every Sunday will screw alot of people up. Shutting down Main would make getting to the Y for a workout a complete nightmare as well.
Shutting down one street is a good idea as you have all the other for people to get in and out of downtown. Shutting down several streets means downtown traffic becomes a crazy nightmare which means it becomes a disincentive for people and businesses to go downtown.
Sweet. San Francisco and Portland already do this and it's really kind of cool. It's nice to be able to walk around or bike around and you only have to watch out for the buses and the light rail.