Well, IÂ don't coast at all, so it couldn't be the opposite for me.
I've never done the outdoor biking for exercise thing, so I'll admit ignorance there. It just seems like those people's legs aren't moving all the time. Also, in my area, it seems like traffic would make it hard to never stop.
I would actually really like the fresh-air aspect, but don't see any benefit (over the stationary)Â beyond that.