At first when I think of the car-free streets I think recreational fun, like back in the day when I was part of the Motor-City Rollers. It was a group of 50-100 people who would converge a few nights a week in downtown Detroit and Rollerblade the city. It was possible because after the 9-5ers went home the streets became a ghost town. Which was AWESOME for us.
But then the idea that someday a safe bicycle commute could really exist like in Portland? I really, really love that idea. Car congestion here is awful and this won't help. But more people used alternative transport? Eh, who knows. Just sounds like a good plan.